It is possible to sever the face off of anything that has one, creating a gruesome mask that can be worn over your own face. This grisly trophy provides a boost to your ego from +1 to +3 depending on the level of the creature it came from when equipped and changes your relationship with the creature's faction or factions by -500. Your own severed face or that of a companion does not cause any reputation drop.

Some creatures have a different name for their "face", but which still functions this way when severed (and is described as their face in the item details).

Creatures whose faction affiliation is overridden by modifications from their base template will provide faces that affect those factions instead of their normal ones; for example, the face of a "dromad trader and psychic thrall" will give -500 reputation with the Seekers of the Sightless Way, not dromad traders. Scaling encounter strength can also increase the ego modifier (it appears to be based on creature level).

Be careful when interacting with face items in your Equipment screen, since unlike most other equipment, the default action for them isn't "remove", but "eat".

Known Faces
Face source Ego modifier Factions affected
Agolzvuv +2 insects, the Girsh
Baboon +1 baboons
Beetlebum +1 grazing hedonists, insects
Cave Spider +1 arachnids
Chrome Pyramid +3 robots
Croc +1 None
Cyclopean Gibbon +2 baboons
Dromad Trader +2 dromad traders
Echelstadt II, High Priest of the Stilt +2 Mechanimists
Elder Irudad +3 Villagers of Joppa
Eyeless Crab +1 crabs
Eyeless King Crab +1 crabs
Gelatinous Ovoid ("sensory bulb", not face) +2 oozes
Goatfolk Savage +1 goatfolk
Goatfolk Thrall +1 the Children of Mamon
Glowcrow +1 birds
Great Magma Crab +3 crabs
Great Saltback +2 dromad traders, tortoises
Honey Skunk +1 hermits
Knight Templar +2 the Putus Templar
Leech +1 mollusks
Leering Stalker +3 robots
Mimic +2 None
Mehmet +2 Villagers of Joppa
Oboroqoru, Ape God +3 apes, grazing hedonists
Ogre Ape +2 apes
Plastronoid +1 robots
Plated Chromeling +1 Barathrumites
Pygmy Forager +1 pygmys
Rhinox +2 crabs
Rocket Turret ("sensor array", not face) +1 robots
Rodanis Y +3 robots, Barathrumites
Saad Amus The Sky-Bear +3 beasts
Salt Kraken +3 Grazing Hedonists, Mollusks
Segmented Mirthworm +1 worms
Slugsnout +1 swine
Slumberling +2 bears
Saw-Hander +1 robots
Snapjaw Scavenger +1 snapjaws
Warden Ualraig +3 Fellowship of Wardens
Warmonger amongst the True (Putus Templar hero) +3 the Putus Templar
Watervine Farmer +1 Villagers of Joppa
Wild-Eyed Watervine Merchant +1 grazing hedonists, Children of Mamon
Worm of the Earth +1 worms