@eri I'm not really sure yet, but here's my best hypothesis:

In ep8, bubble said he's having a baby in a scene where Caine said something to the humans.

In ep9, we see Caine in the void with a faceless floating bubble that does nothing. Maybe Bubble might have sacrificed themselves to make Caine reborn (or maybe Bubble didn't give birth to amything, but sacrificed themselves in some other way to save Caine)

Thats the best I could come up with in a few minutes at least