Phthisic

Each phthisic starts as a suppressed memory or deep-seated fear inside some unlucky person's mind, which a mind reaver of great skill pulls loose and makes physical. The result is a swollen, warped caricature of its source, decorated with ugly extras such as bristly hair, horns or tentacles.

In one round it rakes with two talons for 2d6 each and bites for 1d4. Any creature bitten during a fight saves vs. spell or is feebleminded for 1d4+3 rounds. The worst comes later: once all threats are dealt with and it can feed undisturbed, each bite on a feebleminded victim permanently removes 1 point of Intelligence. It never drains Intelligence while combat continues.

Once each hour, when threatened, it can radiate a supernatural chill for 1 turn, dealing 1d6 cold damage per round to everything within 10 feet; a save vs. breath weapon that round halves it.

Though made of real flesh, the phthisic was shaped by psychic art, so only weapons of +2 or better can hurt it. It heals 3 hit points each round and keeps doing so even below 0 hit points as long as its power source survives. Its nature of turmoil and self-doubt gives every spell cast at it a 25% chance to rebound on the caster, area spells aimed at it included. Feeblemind or confusion deals it 2d10 damage and halts its regeneration for 2d10 rounds.

Wherever it is, a phthisic can see into its lair, and once per 24 hours it can teleport there without error the moment an intruder appears.

It must feed on living minds, yet it cannot go too far from its power source or stay away too long. So it stalks prey at a distance from home, then carries its catch back to devour its consciousness. Lairs tend to be secluded spots near big cities, littered with the shrunken husks of earlier victims, the shriveling being a side effect of these mental meals.

Creating one requires elaborate psionic surgery on a thrall's troubled psyche, and only mind reavers know the technique. They bind the creature's existence to a generative source called a psionic seal, an intricate psionic circuit set into some large, unmoving object. The seal sustains it but confines it to within 3 miles. Destroying the seal destroys the phthisic for good, while killing the person it came from accomplishes nothing.