It's gonna be interesting to see this stuff in tankōbon format.
So, the Hollow creature is called White. Thank god we have a name, now I have don't have to keep calling it the Hollow creature thingy or whatnot - it was like Superchunky all over again, I tell you what. Besides its name, it's apparently based off of a Shinigami's soul (50 points to Lemursrule), which would explain the sealed hole and fighting style. Apparently, Aizen has high expectations for it: if it can't beat a captain-class Shinigami using his Shikai, it's a failure.
Speaking of Aizen, it's been confirmed where he got that cloak from, which is good to know. I also find it intriguing that simply mixing Kidō with the cloak gives you a Harry Potter item. I wouldn't be surprised if that little detail played a role later on. Anyhow, Aizen didn't cut down Isshin with one strike? C'mon, I thought you were better than that, Mr. "I've reached the limit as a Shinigami". Fine, plotkai and whatnot, but still. So, we're seeing a bit more of Aizen's scientist side: he's intentionally allowing unforeseen fighters like Isshin to fight White and unknown variables like Masaki to join the fight, which is reminiscent of how he let Ichigo and co. enter Hueco Mundo to rescue Orihime, something I find interesting.
On the topic of Isshin and Masaki, well, that was one hell of a power (and theory) dampener. Apparently, since Isshin to currently heavily wounded thanks to ol' Aizen, he can't use his Bankai (meaning he can't use Saigo no Getsuga Tenshō, which puts too heavy of a strain on his body, though he seems to be holding his own with just his Shikai. Also, White's Cero seemed to intimidate him somewhat, another indication of White's power. As for Masaki, we finally see her bow (which is kinda lacking in detail if you ask me, much like Uryū's first bow but thinner) and her combat style, at least in part. Letting White attack her so she could put him into a headlock and shoot him with a Hleig Pfeil was a hilarious moment to me (not sure why) and shows how tricky she can be in combat. Also, her arrows are apparently quite powerful if they can produce that kind of effect while blowing through White's head. She seems to have access to a smaller, one-handed version of the bow, just like Ryūken does. Interesting.
So yeah, that's about it for now. Feel free to comment and talk about the chapter down below.