Thanks, I wasn't completely aware of what the Spellplague did. At least the changes for 4e/5e and Baldur's Gate 3 can easily be explained this way. 3e was set before the Spellplague. Back then, some players explained inconsistencies in-game by saying the (2e)multiverse got destroyed after the events of the final adventure Die Vecna Die! and formed anew. I'm quite glad my players were able to stop the rotter before this happened!
