A MONSTERS (Oubliette D&D)
AIR ELEMENTAL Gather the final, rattling breaths of thirteen prisoners who died of lungrot. Seal them in a rusted mess tin. When the tin finally rusts through, the wind that escapes hates the lungs of the living. It has no body, so it steals the breath from your throat to build one.
HD 2 / AC as Chain / Damage 1d6 (Save or spend the next round choking on phantom blood)
ANKHEG The mortar of the deep cells is mixed with bone dust, and the starved things in the walls know it. Blind, pale grubs the size of draft horses. They do not tunnel to escape; they tunnel because they are hungry for the calcium of the dead. The acid they spit smells like old copper and regret.
HD 3 / AC as Plate / Damage 1d8 or Acid (Acid ruins mundane armor instantly)
APE, CARNIVOROUS The oubliette does not have apes. It only has the deepest cages where they threw the strongest men and stopped feeding them. The ones that survived forgot how to speak, forgot how to stand upright, and grew thick, matted hair to stave off the freezing chill of the stone. They still remember how to crack a human femur to suck out the marrow.
HD 4 / AC as Leather / Damage 1d6/1d6 (If both hit, they rend you apart for an additional 2d6)
AQUATIC ELF The lowest levels of the oubliette are flooded with black, stagnant water. The elves down there stretched out even further. Their limbs are like pale ribbons of bloated kelp, their milk-skin wrinkled and translucent. They do not sleep, they just float in the dark, staring upward, waiting for a struggling thing to drown so they can pluck the teeth from its skull to remember it by.
HD 1+1 / AC as Unarmored / Damage 1d4 (They do not strike; they drag you under. Drown in number of turns equal to Constitution)
ABOLETH The original architect of the prison forgot why he built it, so he climbed down into the sump-pit and let the rot take him. Now he is a slug of psychic fat and weeping, lidless eyes. He remembers every sin ever committed in the dark. If he touches you, your skin turns to translucent slime, and you realize you belong down here forever.
HD 8 / AC as Chain / Damage 1d10 (Save or your flesh liquefies over the next three days)