From BRWiki

ALLIP

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.

System Reference Document -> List of Creatures