Download Was Ichigo A Vasto Lorde PNG. Hollows sought a humanoid form but were unable to do so without a strong will. Menos result from hollows growing strong enough that just eating weak human souls is no longer enough for them.
I had to put some work into this after hearing that the series will be getting an official animated ending, after so many years!
It was heavily implied that of all the espada, only the top four (ulquiorra, halibel, barragan and stark) were vasto lorde before they became arrancars (and subsequently espada). In ancient times, hollow evolution was chaotic. Because of their compressed form, vasto lorde have exceedingly dense reiatsu. Only to be reborn as a being of unmeasurable power.