some moons ago, you mentioned that all the gods have returned in one form or another, when i asked about Moander. Was just reading the GHotR and one thing occurred to me: Karsus was also – however briefly – a god. Is he back too? No. Karsus tried to become a god, and some refer to him as 'the momentary god,' but although he seized the POWER of a deity, he never achieved godhood.
He's now a vestige because Ao bound his soul to the Prime Material. Ao also prevented his return in any manner.@Realmslore

— Ed Greenwood (@TheEdVerse) May 25, 2020