Allip

Description

From Mordenkainen's Tome of Foes (2018):

When a mind uncovers a secret that a powerful being has protected with a mighty curse, the result is often the emergence of an allip. Secrets protected in this manner range in scope from a demon lord’s true name to the hidden truths of the cosmic order. The allip acquires the secret, but the curse annihilates its body and leaves behind a spectral creature composed of fragments from the victim’s psyche and overwhelming psychic agony.

Blasphemous Secrets. Every allip is wracked with a horrifying insight that torments what remains of its mind. In the presence of other creatures, an allip seeks to relieve this burden by sharing its secret. The creature can impart only a shard of the knowledge that doomed it, but that piece is enough to wrack the recipient with temporary madness. The survivors of an allip’s attack are sometimes left with a compulsion to learn more about what spawned this monstrosity. Strange phrases echo through their minds, and weird visions occupy their dreams. The sense that some colossal truth sits just outside their recall plagues them for days, months, and sometimes years after their fateful encounter.

Undead Nature. An allip doesn’t require air, food, drink, or sleep.

Insidious Lore: An allip might attempt to share its lore to escape its curse and enter the afterlife. It can transfer knowledge from its mind by guiding another creature to write down what it knows. This process takes days or possibly weeks. An allip can accomplish this task by lurking in the study or workplace of a scholar. If the allip remains hidden, its victim is gradually overcome by manic energy. A scholar, driven by sudden insights to work night and day, produces reams of text with little memory of exactly what the documents contain. If the allip succeeds, it passes from the world — and its terrible secret hides somewhere in the scholar’s text, waiting to be discovered by its next victim.

(From Monster Manual v3.5 - 2003):

The creature that floats before you is like a thing out of nightmare. It has a vaguely humanoid shape, but it’s a shape without features that has been distorted and bristles with madness. From the waist down, it trails away into vaporous nothingness, leaving a faint trace of fog behind it as it moves.

An allip is the spectral remains of someone driven to suicide by a madness that afflicted it in life. It craves only revenge and unrelentingly pursues those who tormented it in life and pushed it over the brink. An allip cannot speak intelligibly. 

Combat: An allip is unable to cause physical harm, although it doesn’t appear to know that. It keeps flailing away at enemies, yet it inflicts no wounds. 

Babble (Su): An allip constantly mutters and whines to itself, creating a hypnotic effect. All sane creatures within 60 feet of the allip must succeed on a DC 16 Will save or be affected as though by a hypnotism spell for 2d4 rounds. This is a sonic mind-affecting compulsion effect. Creatures that successfully save cannot be affected by the same allip’s babble for 24 hours. The save DC is Charisma-based. 

Madness (Su): Anyone targeting an allip with a thought detection, mind control, or telepathic ability makes direct contact with its tortured mind and takes 1d4 points of Wisdom damage. 

Wisdom Drain (Su): An allip causes 1d4 points of Wisdom drain each time it hits with its incorporeal touch attack. On each such successful attack, it gains 5 temporary hit points.