Underdark Monsters
in Old-School Essentials Advanced Fantasy Genre Rules
36 monsters
- Brown Mould - A heat-absorbing fungus that feeds on energy and grows in darkness
- Bulette - Terrifying predator that resembles a gigantic armadillo crossed with a snapping turtle
- Coffer Corpse - Resembles a zombie, a rotting, fetid corpse of the dead left unburied
- Dark Creeper - Short, spindly humanoids with pale skin who wrap themselves in loose, dark clothing
- Deep One
- Drider
- Drow
- Duergar
- Ettin - Large, nocturnal two-headed creatures that live below ground
- Eye of Terror
- Flail Snail
- Flame Lizard
- Frost Toad
- Gas Spore - Strange, non-intelligent fungal creatures that resemble oculus
- Giant Mutant Frog
- Giant SLug - Large boneless creatures that spit acid and burrow through wood and earth
- Gibbering Mouther - A horrible creature seemingly drawn from a lunatic's nightmares with the fluid body of an amoeba
- Gullygug
- Hook Beast
- Hulker
- Krell
- Lurker Above - A subterranean creature resembling a manta ray that swims through the air and drops on prey from ceilings
- Mimic - A master of deception that can assume the shape of any object or creature
- Mind Lasher
- Multichromatic Dragon
- Mycelian
- Otyugh - Large creature with 4 legs, 8-foot diameter body, and 3 tentacles behind its mouth
- Piercer - A cone-shaped shelled creature resembling a snail that hunts by dropping from cave ceilings
- Roper - A 9-foot tall creature that tapers from 3-4 feet in diameter at the base to 1 foot at the top, weighing 2,200 pounds
- Shambling Mound - Intelligent plant creatures appearing as piles of rotting vegetation
- Spawn of the Worm
- Subterranean Lizard
- Svirneblin
- Trapper - An amorphous ambush predator that lies flat and mimics stone floors
- Violet Fungus - A purple to gray fungus that resembles a shrieker, attacks with poisonous tentacles
- Xorn - An embodiment of the element of Earth that glides through stone