Seer: The Obeist Prankster Cat

This is a mysterious, and hilarious, Source-Eater Beast. Legend has it that it was born alongside the world (false) and can grant wishes, though of course that's only a legend.

The poor working cat was dumped into the world of Seer by a pigeon. Loz, dropped onto Weiss Star, exclaimed, "What in the world? Where have I ended up? Is this still another dimension?"

After spending some time on Pugvis Star, Loz was bored out of his mind. When he checked the timeline, he suddenly realized the main story was still several hundred years away, so he chose to seal himself away and sleep...

But one day, a completely silver robot entered the sealed-off place...

The protagonist is practically invincible in the early and middle stages, and invincible in the end.