Abaddon is one of the Cabal, the monstrous behemoths that lie in the deepest parts in the Endless.  The creature was extremely unusual-looking, lacking limbs, head and tail.  Its body was comprised of a huge gelatinous, translucent sphere in the centre of which swivelled a solitary eye.  Abaddon lacked the intelligence of many of its brethren amongst the Cabal, but it was more than capable of meting out a horrifying death to its victims.

At the time of Caliban Grayson's attacks upon the Myr, the Ghul officer Drabella was responsible for Abaddon.