Although Ruby had undergone Berserker transformation, there was still a fundamental gap between him and Ichigo Kurosaki.
That gap meant he could not even withstand a single strike from Ichigo Kurosaki.
"The power has grown stronger again."
Kenpachi Zaraki saw that strike, but had no particular thoughts about the widening gap between himself and Ichigo Kurosaki.
Grimmjow had also awakened, and he joined the Berserkers in wreaking havoc throughout Las Noches.
"What an ugly sight, Grimmjow. Have you betrayed us?"
Tier Harribel blocked Grimmjow's path.
"Hmm?"
Grimmjow sensed something off about Tier Harribel's aura.
"This feeling... I see. You became a Berserker too?"
He burst into laughter.
"No. This is Lord Aizen's ascension for us. It is Berserker transformation built upon Soul Reaper transformation. Because of that, even my Hollow hole has been filled."
Tier Harribel stroked the spot where her Hollow hole had once been. As for what had filled it?
Naturally, it was her own "core."
The defining trait of an Arrancar was that its Hollow mask had been shattered to reveal a human face, and that it carried a blade. Upon release, the Arrancar's Zanpakuto—its power condensed and sealed into a core—would be unsealed, restoring its original form of power. This was known as Resurrección.
Unlike the Soul Reapers, who each possessed a Zanpakuto, Hollows varied in ability and in the density of souls they contained. Thus, even after becoming Soul Reapers, they did not necessarily possess Zanpakuto.
Only Arrancar whose strength approached that of the Espada could possess Zanpakuto. An Arrancar's Zanpakuto was essentially a bladed manifestation of part of its own power, formed by sealing the Arrancar's Power Core.
Therefore, the abilities of an Arrancar's Zanpakuto were often related to the physique and innate abilities possessed by that Arrancar or Hollow, merely enhanced further in