Environment any land (Plane of Shadow)
Organization solitary, pair, or swarm (3–6)
Treasure none

The caterpillar-like tenebrous worm is a voracious predator that hungers for mortal flesh. The tenebrous worm is the larval stage of the gloomwing (see page 133)—but in a strange reversal, these younger creatures are more dangerous than the Adults they grow into. A native of the Plane of Shadow, a tenebrous worm hatches from the body of an unfortunate creature that has been implanted with an egg by a gloomwing. The tenebrous worm is fully grown upon hatching, and immediately begins to scour its environs for flesh to consume.

Although the tenebrous worm tends to be relatively pale-colored, its internal organs seethe and roil with shadowy energies and dark fluids. As the creature feeds, these shadowy innards begin to grow out of its body, forming strange bristle-like filaments of semisolid shadowstuff not only capable of piercing the flesh of those who would attack the worm, but also possessing a deadly paralytic poison. Additional shadowy fluids constantly seep from the worm’s mandibles—when it bites prey, these fluids melt flesh into shadows that the creature can then consume. When a tenebrous worm feeds on enough of this shadowy flesh, the creature seeks out a secluded, shady area (typically just within a cave entrance or in a ruined building) and spins a shadowy cocoon around itself. A tenebrous worm’s cocoon exudes the effects of a darkness spell (CL 8th), muting the surrounding light. After a period of several days, the cocoon tears open and a fully grown gloomwing emerges, ready to seek a host for its eggs.