What if Toriel is already dead before the events of UNDERTALE?
The Elder puzzler seems to be old, and has a liking of puzzles. Toriel aspires to be a teacher. The Elder puzzler dislikes that younger people don’t know how to do “real” puzzles.
What if the Elder puzzler *ed Toriel long ago, and, impersonating her, divorced Asgore, moved to the RUINs and stayed there?
After all, Toriel does tell the protagonist not to return to the RUINs if spared, and her voice can be heard from echo flowers.
Also, the two are never seen in the same room.
So, what if…?