Board Thread:Improvements and Issues/@comment-15519592-20130815082945/@comment-11051098-20130817115200

The voice informing about the evolution of Hollows -> Gillian -> Adjuchas -> Arrancar, is a narrator. It's not Shawlong. You can see that in the manga too, the text on that part is formal.

I agree with SunXia that the flashback is about Grimmjow and Shawlong in particular - Shawlong encouraged/influenced Grimmjow to keep evolving and eventually consume his group so they could help him evolve, which he eventually did. And even though the 4-slot mask Gillian is not named, it is shown in that flashback, which to me indicates that it has something to do with the evolution of Grimmjow or Shawlong. Seeing as its mask resembled Shawlong's Adjuchas mask, I choose to believe that it is Shawlong as a Gillian.

Also, it's stated in chapter 284 that "On the rare occasion when one of the cannibalized hollow's abilities and ego far exceed those of the others, a Gillian that has not yet lost its individuality will appear."

From the text and the mask of the illustrated Gillian that changes into the "4-slot mask", I understand it so that the 1 Hollow that takes control, influences the mask of the Gillian to change. And as all Hollows have different masks, I would say that any Gillian who regains individuality through 1 of the Hollows its made from, will also get individual masks.