Building 10 rooms

CELESTIAL MOSS:  PLANT
SKIN CROCODILE: MONSTER
QUESTING WORM: VERMIN
GREY SATYR: HUMANOID
CRIMSON VAMPIRE: BOSS
WAR COBRA: CRITTER

G F
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I--E--C--D--H
| | | |
J B--A
Room A.
Map room. Globes, nautical charts, atlases, blueprints, guidebooks. CRIMSON VAMPIRE studying X-marked plan of faraway island, so enthralled that it has difficulty noticing PCs. Exquisite rug on room's floor seems like abstract pattern, careful study reveals it to be map of dungeon itself.
Room B.
SIGHT: Walls made of petrified wood, as if you're in the bole of a huge ancient tree.
SOUND: Creepy singing, like every nursery rhyme in every horror movie ever.
Bubbling lake of mildly corrosive alkaline goo must be navigated via stepping stones. QUESTING WORM hidden in goo, obviously. Harmless until you get any blood in the goo, then will go into feeding frenzy.
Room C.
SOUND: Slow, monotonous weeping. Sounds like it's been going for a very long time.
Two statues. One always tells lies, one always tells the truth. They only know things that statues would know. None of the passages out of this room are trapped or dangerous in any way.
Room D.
One passage being slowly walled off by GREY SATYRs under supervision of cranky, half-asleep CRIMSON VAMPIRE who is enforcing compliance w/ threat of physical violence, eternal torment.
Room E.
Time moves slower the closer you get to the middle of this room. SONDRIGHT the INSECURE HUNTER, wearing a crown, wielding BRASS HALBERD caught in stasis at exact centre. In fact crown is cursed - you can remove it pretty easily, breaking the curse and halting the effect, but in the time it takes you several years will have passed outside. SONDRIGHT the INSECURE HUNTER is notorious character from history.
Room F.
Formerly a wizard's study. Now a breeding pair of WAR COBRAs has made a nest of the spellbooks, which reveal interesting magical snippets if closely examined. Torn-up pages, gummed back together, may have produced odd new spells.
Room G.
SOUND: Agonizingly slow waterdrip.
Observatory. Star charts, half-ground lenses, celestial globes, tables of astronomical data (looks like random numbers) and pulsar emissions. CRIMSON VAMPIRE mesmerized by whatever it sees through single enormous telescope. If you broke the telescope's lens you could climb out of the dungeon through it.
Room H.
SOUND: Rumble of tectonic plates shifting, impossibly loud and distant.
SMELL: Faint breeze. Hard to tell where from, seems to change directions.
Enormous mirror is scrying-portal to alternate realms. CRIMSON VAMPIRE 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 I.
SMELL: Acrid tang of goblin shit.
SIGHT: Dust on every flat surface.
UDDIVER the EXHAUSTED WATCHMAN looking for girl/boy/personfriend, who they think is being held captive by GREY SATYRS. Actually came with them willingly to get away from UDDIVER the EXHAUSTED WATCHMAN, now rethinking it, dungeon life losing sense of mystery and grandeur. Still hates UDDIVER the EXHAUSTED WATCHMAN though. Is in room I.
Room J.
TETHYX the EMACIATED COURTESAN attempting to domesticate WAR COBRA, with limited success. Has been reliably informed that WAR COBRA's favourite food is CELESTIAL MOSS, will pay semi-handsomely for samples.