After passing through the Teleport after the Crystal of Life, and then two more doors, there is a lever in a room to the left. Pulling it will open another room on the left, before the one with the lever.
After teleporting and going through the first two doors there is a small button on a southern wall, 2 blocks west of the lock/keyhole. This opens the Hidden room, which is found in the first room after the second door on this level. (Doesn't counts as secret in statistics)
After the first puzzle is an area with some pits. There is a button on the reverse wall of the pillar in the middle of the room which opens the middle of the pillar. Throw a rock across the pits onto the pressure plate to close the pits and access the secret.
In the room after the Crystal of Life with two separated pits, press the button on the wall before the first one. Quickly turn around to face the opposite direction and move three tiles left to cross over the pits before the trap doors reopen. Pressing the button on the wall above the second pit will reveal a Teleport which will take you to the secret.
# In the same room with pits, jump down. First, place a Rock on the pressure plate in the west end of the chamber. There is an area with pressure plates behind grates. Press the button on the wall nearby to disable the Teleport (only works if pressure plate to the west is weighed down) and place rocks on the two pressure plates to open one of the grates. The secret is at the back of the area.
In the room with spiders that resembles the first puzzle, place the torches in the opposite pattern: torches on walls, none on pillar. This will reveal a short passage with a lever and view of the Iron Door. Pull the lever to open the door, to which you can now return. Remember that to close the trap door, take the Rock off the pressure plate used in the pillars of light puzzle.
# On the wall of the room of Secret 7, there is a hidden button which reveals stairs down to a Slime dungeon. On the far right side of the room is a button which reveals a room with the Green Gem. Place it in the mouth of the demon face near the stairs to reveal a large secret room.
In Time and Tide, after pressing the plate before the race across trap doors, turn to the right on the second trap door. There is a button on the wall that opens a wall just ahead with an alternative way, but also with trap doors.
After completing Trails of Thought and reaching the room full of pits and Crowerns, there is a button hidden in the small alcove. Press it and run into the pit area, crossing the closed trapped doors and pressing the button on the wall. The Teleport in the center of the room is gone and the trap door under it is open. Drop down and collect the Gear Key. Returning to the hub room, use the key to open the Iron Door which is located down a hallway to the NE. This is incredibly hard so be prepared for frustration.
In the Catacomb, there is a hidden button in the hall NW of the room with the 4 Undead Soldiers waiting behind a grated door. Press it to open the wall at the end of the suspicious dead-end hallway to the north. You will need to defeat 4 Undead Soldiers then press the button again and rush to enter in time as the door will automatically close.
In the Catacomb, after releasing and defeating the 4 Undead Soldiers behind the grated door, press the button in the area they were in. The grated door will close behind you and the wall in front of you will open.
NE of the room with 9 pits there's a door with 2 buttons and a lever.
Flip the lever down and up, then press each of the buttons in turn.
There is an Iron Door in the level. To open it, as the nearby scroll says, you need to find where the Stone Dragons gaze, meaning you need to find where the gazes of the two dragons intersect. This is just 10 blocks west from the first dragon statue. Stand on that square about half a minute, or so, until you actually hear the door opening, or you can rest and that works too.
On the left wall where you find the Fire Bombs, there is a stone with a rune on it. Press it to open a wall. To pass the grate, put (don't throw it) an object in the teleport that appear when you walk on the pressure plate. When you will take the Orb of Radiance, 2 crabs will appear on the room behind you, even if you put something there. You will have to press the rune stone again to go out.
In the "Maze of Madness" room, where you pick up the Round Key, look at the wall to the right, there lies a hidden button, press it, this disables a teleporter. Make your way back around to the South side of the room, you should see the pillar along the south wall is gone, go forward to find the Pendant.
In the "Walkabout" area, there are three hidden pressure plates when you step on one you'll hear a click, seemingly they do nothing, but there is a trick. Walk around the entire hall clockwise, hitting all three plates, after two times around a Rock should appear. Go around again and a Undead Soldier should appear, kill him. Make one more full pass around the room and the Sack should appear.
Still in the Haunted Halls, north of the pressure plate, there is a stone pillar in the middle of the room. On its east side, there is an hidden button who open on the south-east corner of the Halls. You might have to look for a little while.
# In the Halls of Fire area, drop down into any of the trapdoors. Make your way through the Level 7 area and drop down again. In Level 8, you will find 2 doors controlled by a pressure plate. Drop something on the pressure plate to open the first door, pick it up from the other side to open the second door.
# In the Halls of Fire area, within the Fireball Hallway, there is a hidden button on the east wall, right after the pressure plate.(closer to the head.) Pressing it opens the wall behind you. There you will find another hidden button. Next, locate a third hidden button on the west wall, 2 tiles before the pressure plate. Pressing it opens the wall next to you, there you will find stairs leading to a secret area in Level 5.
In the Halls of Fire, turn north after completing the first challenge. You should see a small rune on the wall. Press it to open a secret passage leading to Level 7 and Fighter's Challenge. You will need Sword of Nex to enter the challenge proper. After you beat Fighter's Challenge, turn your attention to west wall. There is a hidden switch and room with treasure.
In the room south of Crystal of Life, there are 2 pressure plates. Stand on the northern one until the nearby portcullis is completely open, then quickly step south and back north to open two secret rooms.
At the west section of the map, there is a seemingly unimportant area where you can find a Flail. There is a rune symbol on a nearby north wall. Pressing it opens a timed secret door on the passage east of you. You can find a scroll detailing this location somewhere earlier. In the secret room, there is a stairway leading to Level 8Dismantler's Vault.
Opening the Iron Door near the entrance to Level 8 counts as secret. Intercept all the projectiles shot by the three demon heads and the door will open.
In Dismantler's Vault(accessed via a secret in Level 7), in Lightning Conduit tunnel, the third room on the north side of the tunnel has 3 hidden buttons on its walls. Each reveals a pressure plate, upon which you must leave an item to open a secret area in the NE corner of the room.
Also in Dismantler's Vault, at the very end of the Lightning Conduit tunnel, there is a hidden button on the north wall which opens a secret passage on nearby south wall. The last room on the south side of the tunnel has a hidden button which makes accessing this secret possible without getting hit by the lightning.
Finally, entering The Vault itself in Dismantler's Vault counts as a secret. Drop something on the pedestal where The Dismantler lies before picking it up to avoid the lightning traps. There is a switch on the wall behind The Dismantler, press it to open a secret door to get the Golden Dragon treasure.
After solving the teleportation puzzle in the Outer Sanctum, drop into one of the two pits. Behind a grated door there is a scroll with instructions on how to open the door as follows. Place two torches in the wall sconces next to the door and on the wall opposite, stand where the shadows appear to cross, equip 2 stones and throw one North and the other East and the door should open.
After opening the teleportation room that requires two keys from the caverns and the shrine to open, look around the north walls of the teleportation room for a hidden button that disables the teleport and opens the trap floor. Drop down, find the secret, then put something else in the alcoves before taking what is already there to avoid the electric trap.
After you activate the *boss* and go into the teleport,you will see a hall. Complete the puzzle and cross.(comment for how to solve.) Then go to the right of the Goromorg statuette. Look south along the walls and you will find a rune-button. Press it, and a wall will open to your left. There is a Goromorg Miniature on a niche.