Invisible, intangible, and often unknown, the trilloch yet influences things more than many are aware. Unseen to all, this creature makes itself apparent only to those with the aid of detect magic, at which time its true face appears — a pulsating aura of negative energy.
The trilloch was first discovered in the country of Knell on an unnamed Prime world. It was there that it first received its name, a term which in Planar trade roughly translates to "eater of death", referring to its chosen food source: the life forces of dying creatures.
As mentioned, this creature is entirely undetectable without the aid of detect magic or detect undead to spot it; though not truly invisible per se, its form is not material, and can only be noticed as perhaps a vague sense of dread. Even with such a spell, only the most focused segment of its essence can be seen, a rippling aura of energy between two and six feet across. Its full body encompasses a zone 60 feet wide, and it has the ability to feed on the final life energies of any beings that fall dead within this area. Since it can do nothing to harm others directly, however, it's forced to instead push them to naturally kill one another, causing violence and aggression amongst all living things within this radius by pure instinct. It only acts thusly if need be, if the amount of natural death isn't enough to sate its hunger.
Though native to the Negative Energy Plane, trillochs are rarely noticed there, seeming as just yet another gathering of negative energy. Ironically, they're much more commonly noticed elsewhere in the multiverse. Occasionally, a trilloch will find a host of sorts, a being especially adept at bringing about the deaths of others. The trilloch invisibly follows this host, feeding on the carnage they leave in their wake.
The trilloch is not truly malicious, wanting only to feed, but its actions unavoidably bring about harm, and thus many consider it an evil being. This is a misconception; it's as likely to attach itself to a paladin traveling the Lower Planes and smiting evil as it is a warlord wreaking carnage through the armies of opposing nations. All that matters to it is death, and it has no care (nor conception) of the motivation or cause; even an animal could draw a trilloch if it's predacious enough. It can only feed on the dying life forces of sufficiently complex creatures, however. Insects, small worms, and other such creatures do not have enough life energy to feed the trilloch, but any larger and more complex creature is a potential food source for the being.
- Planescape Monstrous Compendium III, pp.108-109