They come from Hueco Mundo, the world of Hollows. Not mindless beasts, but perfect predators: Arrancar. They have torn off their masks to gain reason. Their leader, Aizen—the captain who faked his death, who orchestrated everything from the shadows—reveals his plan. He wants to become God.
A flashback arc, beautifully placed. We see Captain Yamamoto as a young demon with flaming fists. We see the original Gotei 13—not saints, but butchers in black robes who founded the Soul Society on a mountain of Hollow corpses. We learn that peace is only the interval between wars. This arc hums with melancholy. It reminds you that every hero was once a soldier who was once a child who saw something terrible. Bleach - The Complete Series -366 Episodes-
The battle for Karakura Town. Four captains against three Espada. A fight in a forest of jagged stone. Nel, an adorable child Arrancar with a cracked mask, turns out to be a former third-ranked warrior with the body of a goddess and the mind of a broken soldier. The math of power levels becomes meaningless. It is all emotion now. They come from Hueco Mundo, the world of Hollows