There are a total of 22 chapters or missions in Doom The Dark Ages, each having multiple secret areas that you will be able to unlock for additional lore, crafting material, and cosmetics. Accessing all of the secret areas in the shooter is not easy, especially when you don’t know where to look for them.
So if you are looking to make the most of every chapter in Doom The Dark Ages, then the guide below will help you out.
Content:
- Village of Khalim secret areas
- Hebeth secret areas
- Barrier Core secret areas
- Sentinel Barracks secret areas
- The Holy City of Aratum secret areas
- Siege – Part 1 secret areas
- Siege – Part 2 secret areas
- Abyssal Forest secret areas
- Ancestral Forge secret areas
- The Forsaken Plains secret areas
- Hellbreaker secret areas
- Sentinel Command Station secret areas
- From Beyond secret areas
- Spire of Nerathul secret areas
- City of Ry’uul secret areas
- The Kar’Thul Marshes secret areas
- Temple of Lomarith secret areas
- Belly of the Beast secret areas
- Harbor of Souls secret areas
- Resurrection secret areas
- Final Battle secret areas
- Reckoning secret areas
All Village of Khalim secret areas in Doom The Dark Ages
Here is a list of all the secret areas that you will be able to access in the very first chapter of Doom The Dark Ages
Secret Area 1

The first area is located near the beach. While you are heading there to defend it from a demon, you will need to turn right, then jump to the cavern that is under a bridge. You will find it beside a mountain. Head in to find the secret area along with a weapon skin.
Secret Area 2

The second hidden area is accessed with the help of a key in Doom The Dark Ages. The key is obtained from the metal gate that has a neon purple sign on it. You will find it by just following the main narrative. So just interact with it to get the key.
Secret Area 3

The next secret area contains a Codex entry. To find it, you will need to head to the top of a ledge, which is past a narrow path where you will see a lot of debris on both sides. Just climb the ledge and head into the area.
Secret Area 4

As you complete the story of the first chapter, you will find a dead end that gives you a direct view of the white sigil sitting atop a rock in the middle of the sea. Once you reach the edge, you will find a ledge below, jump down, and follow the path to reach the secret cave and a Soldier Collectible Toy inside it.
Secret Area 5

In the village, you will find a vulnerable wall that you can break with your shield. Beyond the wall, you will find the 5th secret area of the chapter.
Secret Area 6

The final Village of Khalim secret area can be accessed after you receive a Blue Key. The Blue Key can be obtained automatically by just completing the main objectives. Once you have it, head back to the starting area of the chapter and then turn left. You will spot a metal gate with a blue sign. Use the key to open it, access the hidden area, and get the Imp Collectible Toy.
All Hebeth secret areas in Doom The Dark Ages
There are a total of 9 secret areas in Hebeth. Here is a list of them all and how you will find them:
Secret Area 1

While making your way to the entrsce of the weapon facility, you will find a barrier that is vvulnerable. Shield back it, then head right after making your wau in. You will find a Life Sigil there and Hebeth’s first secret area.
Secret Area 2

For the next Secret Area, you will need to be near the facility. You will eventually find a place wwhere there are a lot of steam pipes running along the wall. Here you will need to look for a vent that is sitting above some boxes. Once you find it, climb in and you will find a Imp Stalker Toy.
Secret Area 3

Spot a breakable wall with the purple shield icon on it, in the corridor that is outside the research lab. Break it, and then turn left to find the secret area and some gold.
Secret Area 4

When making your way to the research lab, you will need to look for a Sentinel statue that is facing platform that you can access. Your goal will be to climb on the platfrom to find the secret area and some gold.
Secret Area 5

As you complete the story, you will eventually find your way into a room that has a massive helmet hologram. You will need to look for a vulnerable wall here that is next to some boxes. Break it, head in and grab yourself some gold.
Secret Area 6

As you make your way out fo the fascility, look for a run down building. Make yourway inside it through the front door. And you will find a secret area in there with some gold.
Secret Area 7

Look for another vent that is placed near some boxes. Use the boxes to scale it and then head in to find Hebeth’s 7th secret area.
Secret Area 8

The next secret area is also down a vent which is located near the Sentinel Shrine. From the shrine, make your way left down the corridor that’s filled with gore. You will locate a platform there that leads to the vent of the secret area.
Secret Area 9

Hebeth’s final secret area is right outside the main boss room. When you reach this spot, you will find a room whose entrance is guarded by some flames. You will need to extinguish it, but head to the room in the opposite end and then interact with the water valve there. Once the flames die down, head into the room for some gold.
All Barrier Core secret areas in Doom The Dark Ages
There are no collectibles or secret areas in Barrier Core
All Sentinel Barracks secret areas in Doom The Dark Ages
Chapter 4 Sentinel Barracks has six different secret areas that you will be able to access in Doom The Dark Ages. Here is a list of them all and how to access them:
Secret Area 1

When you start Sentinel Barracks, you will be able to spot a breakable wall with a purple shield icon on it. Break it with a melee attack, and gain access to the secret area with the Hell Knight Collectible Toy inside it.
Secret Area 2

You will reach some metallic corridors soon while completing the main objective. You will spot a ledge there which is marked in green, and just above it will be a skeleton with a green glow around it. Throw your shield at it and then teleport to your shield to access the secret area.
Secret Area 3

After progressing through the main missions, you will find a lever, pulling on which will allow you to gain access to a climbable platform. You will then reach an area above the lever, now just follow the path right and you will find the hidden location.
Secret Area 4

While approaching the Dragon’s Den, you will find a climbable platform behind some trees. You will also find a collapsed bridge here. The platform will lead to a sellar with more areas to climb up on. Steadily reach the top to find a Life Sigil.
Secret Area 5

The next secret area of the Sentinel Barrack will be along the road to the Dragon’s Den as well. You will need to look for metal gates and a Ruby Statue located just on the other side of them. When you see it, your next goal will be to drop down to the path that is below the platform that you are standing on. Then make your way along it to come out of the other side, gaining access to the Ruby.
Secret Area 6

The final secret area of chapter 4 is in a settlement that has been set on fire. You will automatically find it while completing the main mission, and you will be ambushed by some flaming skulls here. Spot a fiery tree here, and a flight of stairs behind it. Climb the stairs to find some civilians along with a weapon skin.
All Holy City of Aratum secret areas in Doom The Dark Ages
There are 9 secret areas that you will be able to access in the fifth chapter of Doom The Dark Ages, The Holy City of Aratum. Here is a list of them all and how to find them:
Secret Area 1

When you start the Holy City of Aratum, you will need to look for a massive hole as soon as you land on the first Hell Carrier. Go into the hole and then emerge out into the city from the other end. Then keep moving forward till you find a well that leads underground. Go down it to find some enemies around a pentagram. Take them out to find some health pickups and gold.
Secret Area 2

For the second secret area of the chapter, you will need to get your hands on a Blue Keycard. You will find the card by making your way to a cliff on the western corner of the map. The card will be on a dead body there. Now, once you get the key, jump off that very same cliff to gain access to the new secret area.
Secret Area 3

For the next Secret Area, you will need to make it to the third Hell Carrier. Here you will find a breakable wall marked with a purple shield logo. Break it and you will find a new area along with some loot.
Secret Area 4

After destroying the third Hell Carrier, you will need to head to the platform beside it and keep moving through the corridors till you reach a wooden walkway on the right. You will need to throw your shield to destroy the red chain obstacle. Once done, bash the green box, which will then allow you to climb it and access the wooden walkways that lead to the hidden area, which has a group of enemies surrounding a pentagram.
Secret Area 5

When moving towards the fourth Hell Carrier, you will find a set of metal gates with a Ruby behind them. Now, to unlock the gate, look for the chandelier just on the opposite side. Use the Shield to bring it down and unlock the area with the Ruby.
Secret Area 6

After getting the Ruby, head to the small bridge that is lit by torches. As you move along its right side, you will spot another floor underneath. Jump down and follow the wooden walkway till you find a broken wall leading to another building. Defeat the enemy ambush, and then look for a series of platforms that lead up. Reach the very top to find the Serrat Collectible Toy.
Secret Area 7

When you take down the Titan with the Cyberdragon, you will find a secret platform close to the arena. Use it and move forward to find a metal gate that is locked and requires a red keycard. The card can be found at the bottom of the pool directly in front of it. So just swim down, get the key, and open the gate to obtain a Ruby.
Secret Area 8

The next Holy City of Aratum secret area can be found on the landing zone. Just look for lower levels beside a ledge. You will need to keep descending till you find a wall that has been broken in. Enter it to be able to get your hands on a weapon skin.
Secret Area 9

The final secret area of chapter five can once again be found after you take down the Titan in the city. Look for the stone railings around the area, and then descend down to the lowest level. You will eventually come across a door that leads to an underground area.
All Siege-Part 1 secret areas in Doom The Dark Ages
Siege- Part 1 is the sixth chapter in Doom The Dark Ages, and you will get to access a total of 11 Secret Areas in this mission. Here is a list of them all and how to find them:
Secret Area 1

After you land and exit the barracks in Siege-Part 1, you will need to head left till you spot a waterfall that is right beside the city’s outer walls. You will find the first secret area there.
Secret Area 2

As you complete the main quests, you will eventually come across a group of demons blocking your way. Here, you will need to search for a platform that you can scale up on (it will be on the right). Climb the platform to find the second secret area.
Secret Area 3

The next secret area is right beside the previous one. Just come to the entrance, then turn left and find a locked gate. To unlock it, you will need to find a secret key, whose location is marked in the image above. This area will allow you to get your hands on a new weapon skin.
Secret Area 4

Head beyond the swamp-like area to find a battlefield. You will eventually spot some giants fighting each other here. Once you do, take the path on the left till you reach a narrow passage guarded by a horde of demons. Now look left again to find an underground area. It will lead to a locked metal door that needs the Secret Key once again. Open the gate with it to find a Ruby.
Secret Area 5

Head to the opposite side of the metal gate, and you will eventually find a platform that you can scale up on. Climb it and then make your way along it (picking up armor) to find a group of enemies. Take them out, then head right to find a gold cache at the end of the trail.
Secret Area 6

You will eventually find a Gore Portal when completing the main missions. Enter it, and you will then need to solve a series of puzzles that unlock the central area. Here, look for a couple of boulders, which you will need to climb. At the end, you will find a breakable wall and the hidden area behind it.
Secret Area 7

Head to the eastern corner of the map to find a Sentinel Shrine. Once you find it, keep moving forward, and you will eventually face off against a four-legged demon. Beside the demon, you will find a Sentinel statue, with an entrance below it. Head into the entrance to find the 7th hidden area in Siege-Part 1.
Secret Area 8

The next area is locked behind a metal gate as well, and to access it, you will need to use the secret key. Once you do open the gate, you will find a Slayer toy inside.
Secret Area 9

After defeating the Cyberdemon and Hell Knights, a portal will open up, and once inside it, you will need to go right from the entrance, and find a breakable wall. Throw your shield at it to break it, and then take the door on the right to find a corridor. Once in, look for a red counterweight above, bring it down with your shield, which will lower the central pillar. Now look behind for a green skeleton, which will act as a shield jump point. Use it to jump to the other side and then stand on the edge to find an entrance below. Make your way there to find the new secret area.
Secret Area 10

This secret area is in the swamp region. Here you will find a metal gate locking your access to a gold cache. To gain access to it, you will need to turn left and then move towards the two blue swords. You will eventually find an opening that leads underwater. So swim to the bottom, and then keep moving to come up to the other side. There will be traps along the way, so maneuver around them to reach the cache.
Secret Area 11

In the area where you found the cache, you will spot some scalable platforms on the right. Climb it and turn left. Then smash through the wall to find the final secret area of Siege-Part 1.
All Siege-Part 2 secret areas in Doom The Dark Ages
Here is a list of all the secret areas in Siege-Part 2 and where to find them:
Secret Area 1

The first secret area of Siege-Part 2 is right after you beat the giant titan by using the turret. Head to the remains of the titan and then make your way left to look for a scalable platform. Climb it, then smash the wooden planks to find a box. Head behind the box, and you will find an option to move it. Once you push it, you will find a breakable wall which can be broken with the shield.
Secret Area 2

The second secret area of Chapter 7 can be located above the first one. To get here, you will need to climb the giant box and then use the platform on the right to go up. Now, climb the platform on the left to find a gold cache.
Secret Area 3

While completing the main objective, you will eventually come across a lever that opens a gate on the opposite side of the titan’s corpse. Head through the door, defeat the demons, and you will find a climbable platform which is at the end. Going up, break a chain object, to unlock another set of platforms to scale. Head to the top, and then find a breakable wall behind. Break it, and make your way to the upper left corner to find a Pinky Rider toy.
Secret Area 4

Once you reach the dilapidated castle, you will find a secret key that is floating on the opposite side of the upper level. There is a huge gap, so you cannot get to it right away. Now, stick to the adjoining corridor and then find a breakable wall on the right. Use your shield here to find the 4th secret area.
Secret Area 5

Now, head back to where you saw the floating key. To get it, you will need to head to the second floor and then look for the breakable wall that is near the open balcony. Then continue down the path till you find a Jump Bppste. Use it to reach the other side and get the key.
Once you get the key, jump down to the lower floor and head in the opposite direction of the key’s platform to locate a metal door. Open the door to get a Ruby.
Secret Area 6

There is another locked door nearby. Use the key again to gain access to it as well as a Codex Page.
Secret Area 7

You will eventually find a destroyed hangar while following the main objective. Once you do reach it, you will need to jump to the other side and head to the ship wreckage. You will find a climbable platform here leading to a Ruby Statue around the edge.
Secret Area 8

As you keep going to the next objective, you will find another horde of demons. After you take them out, you will find a scalable platform. Climb it to find a broken wall with a breakable chain inside. Use your shield to break it, and then jump back down from the platform to see that a door has opened.
Secret Area 9

You will find another opening right before you find the 8th secret area. Just climb back down from the platform, and you will find a new open door.
All Abyssal Forest secret areas in Doom The Dark Ages
The Abyssal Forest has seven secret areas that you will be able to unlock in Doom The Dark Ages.
Secret Area 1

When starting out in the Abyssal Forest, you will see that the path forward is mostly linear. However, there will come a time when you see that the path is leading to an elevated area (check the Green Helmet icon). Climb on top there, and you will be able to find the first secret area of the mission.
Secret Area 2

Once you are done with the Forest Gate, you will need to head down the path ahead till you fight a small horde. You will find a set of breakable tree roots here on the side. Break it and you will find a secret area with the Abyssal Forest Codex.
Secret Area 3

The third secret area is behind some breakable roots as well. To find it, you will need to look for a section that drops you below, after passing through a narrow passage. Once you get the path stay on it till you find a Gold cache.
Secret Area 4

Before you go on to secure the Cannon on the Watch tower, you will need to look for a scaffolding that has a breakable metal cross on it. It will have an orange glow, and you can break it with your shield. This will open a secret pathway to an underground level.
Secret Area 5

Travel along the side of the Watchtower, and you will eventually spot a route that drops down at the very edge of the map. So, go down, head through the broken wall, and open the locked door by breaking the metal cross. Head into the now-unlocked room to gain access to the secret area.
Secret Area 6

Head to the edge of the map to find a rotating cover. Break the chain there, and then climb the platforms, which will now be revealed. Now, walk up the stairs and then head across the broken bridges and scaffolding to find the next secret area with a Ruby inside.
Secret Area 7

After fighting off the incoming horde with a Grenade Launcher, you will be able to head through a narrow caravan that leads into the Mines. You will find a green skeleton here that you can use to shield jump off of. Now head to the higher ground and then follow the route to find a Gold cache.
All Ancestral Forge secret areas in Doom The Dark Ages
Here are the nine secret areas in the Ancestral Forge:
Secret Area 1

To find the first secret area in the Ancestral Forge, the first thing you will need to do is find a Secret Key. It’s very easy to spot, and by just completing the main quests, you will be able to spot it. Once you get the key, drop down and then make your way to the Secret Key gate. You can unlock it and then find 50 Gold inside.
Finally, return and then head back to where the first red combat encountered occurred. Here, you will need to charge the Ancestral Heart, then take the top path to find 5 Gold and a gate that you can open to find another 5 Gold. You will pass by a Wraithstone here; however, ignore that for now, as you will need to destroy wolf statues around the map to access this.
Secret Area 2

For the next secret area of the Ancestral Forge, you will need to return to the Sentinel Shrine, which is in the middle, and then head down the path from the very beginning of the level. Open the locked gate here with the secret key to find a Wold Statue. Destroy it with your shield.
Secret Area 3

Make your way towards the Ancestral Heart, then head down the path that is towards the lower left. You will find a green skeleton here that you can use the Shield on to get a jump. Use it to head up and then get your hands on some gold. You can get the crane to drop a Life Sigil here.
Secret Area 4

Head forward from here till you find some gold, and then drop to the right. Take the drop, and it will lead you to a Gold cache.
Secret Area 5

From the Ancestral Heart, take a few steps to the right and you will be able to jump across the gap to find some gold. You will also find a Secret Key gate here, so use the key to open it and get your hands on a Ruby and a Toy.
Secret Area 6

After taking the elevator to the Ancestral Forge, you can move forward, but before entering the tunnel, you will find a breakable wall on the left. Smash it with your shield, then break the orange chain to open the gate there that has a Ruby inside.
Secret Area 7

From the Ancestral Forge, head into the tunnel, then head straight till you drop off a ledge. Now, turn around and you will find a blue gear here. Use the shield to hit it, raising a platform that allows you to jump across for a Gold Chest.
Secret Area 8

Keep crossing the platforms till you reach a small wall. Climb over it, and you will find a ledge, which will drop you to the secret area.
Secret Area 9

For the final secret area of the Ancestral Forge, you will need to climb to the top of the platform in the same area and look for an orange chain. Break it, and then jump across to find a blue key. Use your shield on it to raise a platform, then jump across the ledge, where the orange chain has broken. Now, grapple onto the two green corpses to find a Codex Entry and a Weapon Skin
All Forsaken Plains secret areas in Doom The Dark Ages
Here is a list of all the secret areas that you can access in the Forsaken Plains:
Secret Area 1

After you spawn near the Castle, the first thing you will need to do is kill a few monsters. Once they are dead, you will notice a green corpse on the side. Use it to grapple onto the isolated platform and then keep going across the elevated platforms till you reach the first secret area that is marked with a Green Helmet hologram.
Secret Area 2

The second secret area is found after you have killed the first Leader and wave of enemies near the Hell Cannons. You will find an elevated area on the edge of the map here. Climb up it to find the area. However, do keep in mind that you will be ambushed by another wave.
Secret Area 3

After taking down the second Leader, make your way inside the small cavern, which is on the side. You will find a green corpse there that you can use to grapple onto the platform in the level above. You will find a Green Helmet hologram here.
Secret Area 4

Head to the Statue marker, which is next to the Purple locked gate. Here you will need to drop down near the edge and then take a jump cannon to reach the floating platform infront. You will find the Cyberdemon toy here.
Secret Area 5

Near the Statue marker, you will find a locked room with a secret Purple key inside it. You can get here by using the green corpse on the side. Once in, you will need to break the metal chains to open the locked upper door.
Now, drop down from the door to get the key and then use it to open the locked Purple door. Head in, beat the enemies, and get the Roby from the statue.
Secret Area 6

The sixth Secret Area of the Forsaken Plains is behind the locked Purple door where you fought the Leader. You can use the key you just obtained to enter it. Now fight your way through to the Ruby, and then break the chains at the end to create an exit.
Secret Area 7

After securing the Core, beat all the enemies in the large arena, and look for a Purple Locked Door near the Atlan. Unlock it with the Secret Key to find the Prince Ahzrak Codex inside.
All Hellbreaker secret areas in Doom The Dark Ages
There is only one secret area in Hellbreaker
Secret Area 1

Once you get out of Atlan, turn around and try reaching its head. The head is the secret area which contains a collectible toy.
All Sentinel Command Station secret areas in Doom The Dark Ages
Here is a list of all the secret areas that you can gain access to in the Sentinel Command Station:
Secret Area 1

When you leave the ventilation shaft, head forward till you find a hole in the wall on the right. Head in to find some gold and a Codex Entry.
Secret Area 2

Keep heading forward till you fall down into the Control Room. Here on the left, you will find a breakable vent cover. Use your shield to force it in. You will now reach the second secret area, where some demons will ambush you. Kill them to gain some gold and a Weapon Skin.
Secret Area 3

The third secret area is unlocked after you have interacted with the second console. You will now gain access to a ventilation shaft. So, climb into it and then turn right for some gold. You can turn right again for a Life Sigil.
Secret Area 4

As you complete the story missions, you will eventually make your way up an elevator, then come across a gap that will prompt you to perform a Shield Jump. Once you make the jump, head to the end of the corridor till you drop into a hole to find some Gold and a Ruby. You can push the crate to come back out.
Secret Area 5

When you get the Yellow key, open the elevator gate and then jump across the gap for a Gold cache. You can then jump down the elevator shaft to get a Shield Rune and activate the jump pad below.
Secret Area 6

From the previous Gold cache, you can turn around to find a ventilation shaft that has a breakable cover. Break it, and head down the shaft, then climb the wall. You will find the spot here that has a Life Sigil.
Secret Area 7

Break your way out of the ventilation shaft. You will be faced off against some demons. You will need to kill them to get a Secret Key. The key then gives access to two Secret gates in the mission.
Secret Area 8

Once you get the Secret Key, head out of the room and then to the right, you will find a Secret Key Gate. Unlock it and then kill the Agaddon Hunter to get a Wraithstone.
Secret Area 9

Head down the elevator shaft this time, and then get the Shield Rune. Now finish the final red combat encounter and head to the final Secret Key gate to find a collectible toy inside.
All From Beyond secret areas in Doom The Dark Ages
There are no secret areas or collectibles to be found in the From Beyond mission.
All Spire of Nerathul secret areas in Doom The Dark Ages
There are a total of 11 secret areas that you will be able to unlock in the Spire of Nerathul:
Secret Area 1

Once you take out the Komodo Champion, you will need to make your way up the hill, which is on the left of the island. Once you reach the ledge, drop down and you will find a Gold Cache there.
Secret Area 2

Once you get to mount your dragon, head to the large mountain outside of the map. You will find a Titan there. Kill it to reveal a lanfinf zone. Now kill all the demons in the zone to get your hands on a Wraithstone.
Secret Area 3

Head to the centre of the map and dive into the landing zone leading to the depths. Once you are in the underwater tunnel, you will find some Go;d. Now keep following it to the end and then surface to find yourself in a gated building that you passed by. You will find a Ruby here.
Secret Area 4

While progressing through the story, you will finally reach a ramp that will lead you to a spiral staircase on the right. You will head up the stairs to find a secret area with some gold and a Sentinel Shrine.
Secret Area 5

Use the teleporter to travel to another area where you will be swarmed by imps. Take the imps out, and then press through the area to find a Weapon Skin and a Wraithstone.
Secret Area 6

Once you are back on your Dragon, you will eventually find yourself flying down a tunnel till you reach a landing zone. Here, you will need to progress till you reach a jump pad and then a green corpse that you can grapple onto. Now go further into the room before heading down, and you will find a breakable wall on the left. Destroy it with your shield, and you will find a Collectible toy inside.
Secret Area 7

After the previous secret area, make your way down the ramp and then step onto the bridge. There, you will notice a jump pad to your right, now look down and you will notice another jump pad along with an explosive barrel behind a wall. Shoot the explosive barrel to destroy the wall, then head down to find a Gold cache.
Secret Area 8

Make your way through the destroyed ship till you reach a room that has a lot of Imps and explosive barrels. Now head up the ramp to find an orange chain above. Break it with your shield to drop the crate. This will then raise the gate that is opposite to you. This will then lead to a jump pad, which will then launch you up for some gold and a Ruby.
Secret Area 9

Continue through the destroyed ship till you drop down. Now turn around and head to the ledge to drop down again. You will now find 18 Gold and a Life Sigil. You will also be attacked by a Komodo Champion.
Secret Area 10

Head to the Sentinel Shrine, and opposite it, you will find a building with a pathway underneath. Head to the underpath, and you will find some Gold and a Life Sigil there.
Secret Area 11

Once you deactivate three Statis Emitters, you will unlock another dragon landing zone. Now head down the ramp and then turn around to spot another ramp that leads underneath onto the other side. You will find some gold here, and from there, climb the wall to go up the tower, use the jump pad, and then drop down to a ledge. Now, turn around, and there will be another ledge with some armor shards that you will be able to jump to. So make your way across and go along the way to find a Collectible Toy.
All City of Ry’uul secret areas in Doom The Dark Ages
Here are all the secret areas in Chapter 15, the City of Ry’uul:
Secret Area 1

The first Secret Area is found near the first Shield Charge ring. Instead of launching through it, you will need to drop over the ledge, then break some bramble with your shield and reach the area to get some gold and a Purple Stone.
Secret Area 2

Using the Purple Stone from the first secret area, use it to open the gate and activate a jump pad which is on the opposite side. Now, use it to jump up and obtain a Ruby.
Secret Area 3

After you launch through the first Shield Charge ring, you will need to climb the wall to spot another ring. However, do not go through it just yet. Instead, walk to the ledge and then drop off it for some gold and a Life Sigil.
Secret Area 4

Continue with the main missions till you open a gate and pass through a point-of-no-return. Here you will need to cross the gap and use the jump pad to go up a floor. Now head up the stairs, where you will see a green corpse. Don’t use it for a grapple just yet. Instead, turn right and then drop down the ledge for some gold. Then climb the wall and get your hands on a Codex Entry.
Secret Area 5

Head back up the stairs and then grapple onto the green carcass to reach a Gold cache.
Secret Area 6

Right after getting the Dreadmace, head into the next room. You will find a blue gear there that you can use your shield on. Use it to raise the platform and then head into the water underneath to find some gold and a Roby, which is behind a gate.
Secret Area 7

After your next red combat encounter (with a Cacodemon), keep going till you start to swim up a tunnel till you find a Purple Stone. Now, swim to the opposite end, and head through some fire launchers to find gold and a Life Sigil.
Secret Area 8

Head back to where you found the Purple Stone, and then activate it to take the lift up. Then go down the corridor till you drop off a ledge. Face off against the demon there and then find a Gold cache.
Secret Area 9

After using the next Shield Charge ring, climb onto the next wall till you walk off the ledge. Then, infron you will drop down to a lower platform. You’ll grab some gold here and then launch through the next ring to land beside a Gore Nest. Destroy it and then defeat the Hell Knight miniboss. This will net you a Demonic Effence.
Secret Area 10

Head back up the wall and through the doorway to reach the starting room. To the right you will find some debris you can break through, so use your shield on it to find yourself a collectible toy.
All Kar’Thul Marshes secret areas in Doom The Dark Ages
There are only 5 secret areas that you will be able to unlock in the Kar’Thul Marshes:
Secret Area 1

When the mission starts, head right, and then jump onto one of the platforms. From there, head left and then look for a blue eye through the wall. Through your shield, and it will open a gate where the first enemy spawned. Head there to find some gold and a codex entry.
Secret Area 2

Head to the far right of the map, where you will get to enter an area in the game. Now move forward, and then turn around after a while to find a secret area with a Gold Cacher.
Secret Area 3

Head to the location shown on the map above, and you will find the entrance to a hidden area there. Once in, you will you teleported to a room which has a closed gate on the other side with a pool in the middle. Now jump into the poo, and then dive to the bottom, and you will eventually reach a platform. From here you will need to throw your shield behind he closed door. So jump down from the platform and aim for the pedestal with your shield. Once you did it, dive into the pool again and fall onto the platform. You will now gain access to the secret area with the Ruby inside.
Secret Area 4

From the second Wolf Statue, you will need to turn around and then climb up the wall. From there, head left, and straight ahead, you will find some gold. From here, keep moving forward till you drop down into a cave. You will find 3 gold on the right, along with a path that leads to a third Wolf Statue.
Secret Area 5

The final secret area is near the fourth wolf statue. From here, you will need to turn around and follow the path till you reach a big gate. Enter it, and find yourself in a rotating tomb. To rotate it, you will need to throw a shield at the blue eye, which is infront of the room. To proceed, you will need to make it so that the water area is on the right and a single block in the middle of the room. You will find a Gold cache here.
All Temple of Lomarith secret areas in Doom The Dark Ages
Here are all the secret areas in the Temple of Lomarith
Secret Area 1

Keep following the main path till you reach a big green portal right after a small bridge. Here, you will need to beat all the enemies and then turn right instead of entering the portal. You will eventually come up on another bridge. Throw your shield there to jump on and then collect the Gold and the Ruby.
Secret Area 2

Once you pick up the Ruby, you will then need to proceed through the main story by going through the portal. Now swim through the waters, and once you reach the sunken shipwreck, swim through it, but before exiting it, take a right. You will find the secret area with a codex entry.
Secret Area 3

After you obtain the codex, you will need to leave the area through the portal. Then follow the path till it drops down into the water. Now swim down and then take a right. You will eventually notice a lamp with a hole beside it. Swim into the hole and then keep following the path to find the third secret area
Secret Area 4

After beating the leader, you will find a breakable wall near the main objective. Use your shield on it and then go in to get your hands on a Gold cache.
Secret Area 5

As you keep progressing through the main missions, you will reach a point where you will have to shield-bash your way through a green ring. Once you do, defeat the enemies there and then take a left before the next ring. Destroy the wall there to find some more gold.
Secret Area 6

Once you go through the second green portal, you will come across a swimming section. Complete it, and you will reach a new area where you will need to beat all the enemies. After you are done with them, head left and enter the portal. Here you will find the third and final underwater secret. After you get down, use the jump pad to reach a weapon skin.
Secret Area 7

Once you get the weapon skin, make your way back outside through the portal. From there, turn left to see a shipwreck and a breakable wall inside. Break the wall, head in, and hit the eye symbol with your shield to open the gates. You will find a Gold Cache there.
Secret Area 8

Now make your way down the ship till you reach some stairs. From here, turn around and enter the ship this time. Keep following the path, and head inside to find some enemies. Once you beat them, drop down, and you will find yourself a Wraithstone.
Secret Area 9

Exit the ship and then head up the stairs. Once you reach the mid-point, you will need to jump off to the right and then head forward to find some gold on the ground. Now jump off the right side again and keep moving forward till you find some scalable platforms. Get to the top and then turn left. You will come across a Sentinel Shrine, and to its left, there will be a door, which can be accessed with the secret key. You will find a Ruby in this Secret Area.
All Belly of the Beast secret areas in Doom The Dark Ages
There are only six secret areas in Belly if the Best:
Secret Area 1

After killing all the enemies in the first red encounter, you will need to interact with the organ to progress the narrative. Once that is done, turn left to find a Gold cache.
Secret Area 2

From the Gold cache, turn left to find the door that leads to the next main objective. Instead of going through it, stick to the left wall till you find a green corpse above. Use your shield to grapple onto it and get your hands on some gold.
Secret Area 3

Once you reach the next area, stick to the middle of the room and look for a breakable wall on the left. Use your shield on it to grab some gold, and from there, look up and then throw your shield at the blue symbol, and then quickly throw your shield at the green one to reach the area. From there, turn right, and you will see the ruby on the right. Now, climb the wall, then go left and turn around, and keep following the path to get the Ruby.
Secret Area 4

After getting the Ruby, continue with the story, and once you have destroyed the second part of the organ, you will then need to turn right and spot a green statue there. Throw your shield to it to grapple, and then up over the platform to get the Gold Cache.
Secret Area 5

As you complete the story, you will eventually come back to the place where you destroyed the first organ. Now, keep following the marker till you reach a big hallway with a lot of enemies. Beat them, collect the codex that is behind, and then jump down from the ledge that is infront of the codex. You will find a blue symbol on the right, hit it with your shield, and then head inside to find some gold. Now drop down the hole that is behind the hole. This will trigger an encounter, complete it to pick up the toy collectible.
Secret Area 6

After completing the encounter, leave the area through the portal. Now follow the wall on the right to go through an opening in the wall. You will reach a room that has a blue symbol above. Throw your shield at it and then go through the unlocked hallway. Collect the gold on the way and then climb the wall to find the secret area.
All Harbor of Souls secret areas in Doom The Dark Ages
There are a total of 10 Secret Areas in the Harbor of Souls:
Secret Area 1

After the corridor, when you reach the room, you can turn around to see some gold in an area above the entrance. So just jump there to collect it.
Secret Area 2

Once you pick up the gold on the bridge, you can move ahead, and in the next room, you will find a switch on the right side of the wall. Hit it and then turn around, and head around the block, you will notice that a lot of enemies have spawned. Kill them and then use the elevator to reach the secret area and get the gold.
Secret Area 3

From here, keep going ahead till you see a moving trap platform that is going up and down. Head onto the platform and then turn right. Jump to the platform on the other side and stand on the pressure plate. When you do that, turn around and hit the blue symbol with your shield to unlock the gate below it. You will find a ruby there.
Secret Area 4

From the Ruby, turn right and then go down the stairs. Here you will find a blue jump pad. Here, you will need to jump over the ledge to the cliff there and find a gold cache and the next secret area.
Secret Area 5

After getting the Blue Skull, when the story progresses, you will need to jump down from the ledge and then turn left. Now, keep heading forward till you find a climbable wall. Scale it and then turn right to see a blue skull gate. Head past it to find the gold and a toy collectible.
Secret Area 6

Drop down the ledge that is behind the gold. Then follow the path to get onto the jump pad, which is at the end. You will use it to reach the secret area.
Secret 7

After finding this secret area, keep heading down the main path to find a red enemy encounter. Defeat them, then keep heading forward to reach a round staircase. Under the staircase, you will need to break the wall, then throw your shield at the blue symbol. Once you do, get into the elevator in the middle of the staircase. This will take you to the top, where you can make the jump to a nearby Wraithstone.
Secret 8

After picking the red skull, continue with the story till you reach a green statue that is above you. Climb up the wall using it, and you will find a secret area with a gold chest inside it.
Secret Area 9

As you continue on the main path, you will reach another moving block, which has another moving block behind it. Step onto the one that is behind. Then, when it reaches the top, jump over to the bridge to reach the gold.
Secret 10

Now, following the quest marker, you will eventually reach the other side of the room. You will need to move one block here, and below it, you will find a breakable wall. Shieldbash through, and you will find a Gold Cache here, along with completing the “Dragon Hoard” challenge
Note: The article is a work in progress! We will update the list after we unlock all the secret areas for chapters 20-to-22.