Daemon Bone
Haven taken a hint from the Necromancers, the Cabal found that Bone does, indeed, retain it's tie to life. It is even useful in the ritual of of binding when enough power is at hand. Daemonic forces are summoned and controlled by use of this reagent.
Bring 1,000 such bones (dropped by the monsters found in Doom) to Victoria the Sorceress (located in the same area) to receive a Golden Skull. Bring this to Chyloth the Ferryman to access the deeper areas of the dungeon, where the Dark Fathers can be found.
Daemon bones originally appeared in the single player Ulitma games as a Sorcery reagent, and were to have been used in Ultima Online as a reagent for the (originally canceled) Necromancy system.