According to the canon of In Nomine, Abaddon is one of the main regions of Hell. A blasted wasteland, where Saminga has built his bone citadel, but which has otherwise been left untouched by the other Superiors.
That is, in itself, rather significant. If there’s one thing that has been established inside of In Nomine, it’s that the Superiors are constantly jockeying for position, yet one of it’s provinces was left empty for millenia. Saminga was one of the last of the “old Princes” to be named.
But it should also be noted that Saminga has a thing for death and the dead.
According to the Abrahamic traditions, Abaddon is not just a place of perdition, but also an Angel of Destruction (or more recently an Angel of the Pit).
So perhaps Abaddon is not just a place in hell, but the very body of the Fallen Angel Abaddon.