The Bleach: Thousand-Year Blood War anime is full of surprises as the Soul Reapers and the villainous Quincy Empire fight one last battle for the fate of the Soul Society. Both sides are using powerful secret weapons never before seen, such as the Quincy Medallions and even Rukia's very own bankai. Now, the Soul Reapers and Sternritter are fighting to see who has the best zombies.
Source：https://www.cbr.com/bleach-mayuri-four-arrancars-explained/
