User blog comment:Xilinoc/Ch. 666 (NOT YET RELEASED)/@comment-9282993-20160317113347/@comment-3230060-20160317131925

So I'm not expert, but here's how it looks to me. Grimmjow helped train Chad and Big Boobs. And he was asked to help Urahara with one of his many possibility plans. In exchange it appears Urahara has pushed Grimmjow to his beyond normal Arancar levels.

Aizen removed their mask is basically like saying making them Arancar.

His reiatsu being full hollow again. Well I assume that's kinda what it means to take that final form. The arancar seems to be part shinigami cause of the whole sword and stuff.

Again, not an expert. Just what I THINK is happening. Here's hoping I didn't just make a fool of myself.

P.S. Sorry for spelling, it wasn't ever my strong suit, much less another language.