Building 7 rooms

BLUE BLOSSOM:    PLANT
TOTEM LEVIATHAN: MONSTER
STAR LEECH: VERMIN
NIGHT GNOLL: HUMANOID
PROBLEM CYCLOPS: BOSS
MAGMA BOA: CRITTER

G C--D
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E--A--B
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F
Room A.
Cube-shaped room w/ square sliding puzzle on plinth in centre. Fetching missing piece from room B and solving puzzle will completely reconfigure dungeon, reality around PCs. Roll a new dungeon, place PCs in random room.
Room B.
SOUND: Sound like crunching glass or gnawing teeth. Comes from within walls.
High ledge w/ two entrances that looks out over vast lake of lava. One NIGHT GNOLL peacefully fishing w/ brass rod, wire, hook. If left alone long enough he will catch something. 50% chance of hungry lava fish, 50% chance of lava treasure.
Room C.
Spiral staircase. Young NIGHT GNOLLs sliding down bannisters. Will run away if they spot you, bring back angry parents.
Room D.
SOUND: Creepy singing, like every nursery rhyme in every horror movie ever.
Enormous mirror is scrying-portal to alternate realms. PROBLEM CYCLOPS getting stern lecture from overboss in Plane of Chaos/other, better dungeon/Hell, will shortly emerge in extremely foul mood. If there is a mirror anywhere else in the dungeon this mirror will let you look out of it.
Room E.
TETHIVER the GREEDY CHAMBERMAID and ZERKWOMP the RHYMING CHAMBERMAID fighting for possession of a TOME OF THE SWARM, each with an extremely good argument for why it is rightfully theirs. Actually they stole it from the hoard of a PROBLEM CYCLOPS, who had it as a birthday present from their underworld pen pal and to whom it is of great sentimental value.
Room F.
SIGHT: Room is part of ancient mansion, walls are rotting wood.
SOUND: Creepy singing, like every nursery rhyme in every horror movie ever.
Pit with STAR LEECH lurking at bottom. V. poorly concealed. A couple of gold coins and a BRACELET OF THE LICH in extremely poor condition gleam among the bones of a dead adventurer.
Room G.
SOUND: Boom of distant explosions, clatter of drills.
Bunch of NIGHT GNOLLs quivering in fear as you approach. TOTEM LEVIATHAN followed you in, is directly behind you.