Building 10 rooms

PIRATE SLIME:    PLANT
CLOAKED PHOENIX: MONSTER
SINGING MOTH: VERMIN
VIOLET ZOMBIE: HUMANOID
HOWLING TROLL: BOSS
DUSK RAY: CRITTER

F--G
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I--B--D--E
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J--A
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C
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H
Room A.
CLOAKED PHOENIX asleep in centre of irregular room, can only be squeezed round w/ difficulty.
Room B.
Big circular room, HOWLING TROLL armed with PIKE OF THE DAMNED patrolling boundaries. HOWLING TROLL will not allow anyone to pass straight through crossroads. Doesn't mind you turning corners. Cheating by trying to turn two corners will be strictly punished.
Room C.
Stepping stones over slow-trickling underground river. Actually pretty easy to cross. DUSK RAYs drinking at edges, not aggressive unless provoked. Easy to provoke though.
Room D.
SIGHT: Empty, rusted iron cages hang from hooks in the wall.
FENDISSON the CURSED PALADIN, wearing DANCING NECKLACE, meditating atop stone pillar to unlock its full power, which they intend to use to conquer world.
Room E.
SMELL: Strangely cold, like being in a meat freezer.
SIGHT: Walls are sandstone, gritty when you touch them.
Single enormous carnivorous PIRATE SLIME that is secretly intelligent and the mastermind behind everything that happens in this dungeon.
Room F.
Old wooden chest, given wide berth by nervous, prowling VIOLET ZOMBIEs who are 100% certain it's a mimic. 20% chance this is true. Key to chest, even if it's a mimic, is clutched in the hand of the top half of a skeleton in room J. Chest contains reasonable amount of gold, partially-chewed WOODEN CORONET (operates at half efficiency until repaired), gnawed bottom half of skeleton. Possible if chest not mimic that it will follow PCs around dungeon fucking w/ them.
Room G.
Apparent dead end in VIOLET ZOMBIE workshop. Secret door concealed beneath anvil. VIOLET ZOMBIE blacksmith not pleased to see you, will attack with half-forged GIANT'S KNIFE, only continue to forge it if compelled. Possibility that PCs emerge from beneath anvil.
Room H.
Space is bent in such a way that walking down this tunnel will bring you out in room F.
Room I.
Cornered, enraged, only semi-wounded CLOAKED PHOENIX preparing to unleash its ultimate attack on bunch of spear-wielding VIOLET ZOMBIEs who think they're doing much better than they are. If you wait you can get it before its ultimate attack recharges.
Room J.
Formerly a wizard's study. Now a breeding pair of DUSK RAYs 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.