The backstory is a Merging the Branches version of The Consuming Shadow where all four protagonists were a team
Trying to avoid specifics since Existentially Challenged just came out and some of the clues are major spoilers:
Elizabeth's version of the story suffered from her limited perspective, but there are enough clues to slot it into place. Diablerie's real identity was the Warrior, Elizabeth's predecessor was the Ministry Man (Mister Teapot fitting neatly with T), Diablerie's magician friend was the Scholar. The one that's most blatant is a character who has only been suggested; somebody is drawing Diablerie's runes for him without going insane, and that was the Wizard's special ability.
