Let's say that you become a petitioner in the Citadel of Slaughter. Eventually you die.
Do you, as a petitioner:
Stay dead (oblivion)?
Come back, fight a whole lot, then eventually die again? (Sort of like a much darker version of Valhalla.)
Merge with the realm itself?
Merge/become one with Erythnul?
Or something else?
From the description given of the citadel, saying that it has an endless stream of petitioners, that would lead me to believe that they are brutaly evicerated only to rise again later to rejoin the endless battle and do it all over again. Like you said, a sort of insane,dark Einheriar constantly hunting and slaughtering each other.
Planescape translated:
Bariaur eyeing the two humans looking at his wares-"Hey!Try and peel me and I'll have ya scragged addle-coved clueless!"
Thief to Mage-"I think that weird centaur thing just called you a retard..."
Actual gameplay conversation