D'Compose is simply an undead Inhumanoid, possessing flesh-corrupting talents and heliophobic weaknesses akin to those of a vampire. His unique appearance is marked by a dinosaur-like head and an exposed chest cavity whose gated ribcage can swing open to jail his prey. With the mere touch of his decrepit claw, D'Compose can turn his victims into frightening "undead" monstrosities (usually enlarging human victims to a gigantic size in the process) and they revert to normal only when exposed to daylight (known to the nonhumans in the series as "whiteburn"). He resides in the subterranean kingdom of "Skellweb," where he commands a massive undead army. Skellweb appears to be close enough to the surface that Earth Corps is able to drill through its upper confines on two occasions to allow sunlight to penetrate.