[ Loki shoots Thor a dirty look even as he responds. ]

Xistentia. A waystation between the different universes and realms. I assume you remember those from your studies.

[ A pointed tone there to illustrate Thor's ability to retain factual knowledge from their childhood. ]

It seems the multi-universes are crumbling due to an outside virus or organisation. Much like the Dark Elves, they wish to return to the nothingness.