i'm trying to figure out why and when the vast glub happened. if gl'bgolyb glubbed because feferi left for the medium, then how did fef prototype her? if gl'bgolyb glubbed before feferi prototyped her and went to the medium, then why did gl'bgolyb glub?

It’s not confirmed how glubglub died, but it’s implied that she got hit with a meteor, released the Vast Glub, died, was prototyped, and then entered with Fef