Hallibel attempts to strike back at Aizen but only hits an illusion and he kills her. He then turns to the shinigami and vizard.
In Hallibel’s past, it is revealed that she was a Vasto Lorde gathered three other hollows, Sun-sun, Mila Rose, and Apache to work together and defend against other hollows. Barragan tries to force Hallibel to join his army, but she is defiant. A partially transformed arrancar with cracked masks from Barragan’s army attack them and almost defeat them, but Aizen intervenes and kills him, asking Hallibel to join him.
Aizen cuts down Hallibel, claiming she isn’t strong enough to fight for him and further sacrifices would achieve nothing. He claims he didn’t plan for his outcome after going through so much trouble to gather the Espadas. It implies that he was hoping the arrancar could do more than they did, but in the end, they didn’t really do anything to affect the story aside from roughing up a few of the good guys. This episode itself was not in the manga I think, and mostly just showed flashback of Hallibel’s past; it didn’t add anything to the plot, but did give some character development to her. It’s implied that she was a Vasto Lorde, which I don’t recall seeing anything about in the past. But if so, it means some of the other Espada were probably also Vasto Lorde, and they honestly… aren’t that good. I have a hard time believing that is true though, as supposedly the Vasto Lorde are strong enough to take out Soul Society. The credibility of filler is always in question, but I still doubt they’d go directly against canon information.
The episode also showed Hallibel’s fraccion in their pre-arrancar forms, but I couldn’t really bring myself to care about long dead characters who didn’t do anything significant. Clearly however, the transformation to arrancar boosts power by a large amount as evidenced by the one random partially transformed arrancar. The four of them went from strong hollows (still trash) to ones with all sorts of special powers who could compete with officer-level opponents. To me at least, it seems hollow to shinigami gives a far greater power boost than shinigami to hollow. The vizards’ masks apparently only gave them a mild speed and endurance increase plus the ability to use ceros (which is again too weak at this level). Of course, some people will say you can’t judge that much from fillers, so I’ll just leave it at that. Most of the episode was pretty poorly done and boring, along with the usual bad art and character designs often seen in fillers, but Aizen does seem to be finally going into action at the end.