There have been several times in history where there were antipopes, and at least twice have there been three popes at once. This happened for various reasons, but it always started when one group of cardinals elected one person, and another group elected another. The longest time in which there were multiple popes was the Western Schism, which lasted 40 years. The popes also repeatedly struggled with the Holy Roman Emperors, although after the start of the Renaissance the old rivalry slowly died out.
A Bankai is the powered-up form of a magic sword wielded by a Soul Reaper, a militarized death god from the anime Bleach. I haven’t actually seen any Bleach, but I’ve watched enough shonen to understand how such things go down. In fact, the least realistic part of this comic is the popes all working together.