To anon who asked where Kenjaku got the cursed energy to start the culling game. He didn’t need that much cursed energy to start it, he needed the results of the culling game to generate enough cursed energy to trigger the merger between humanity and master Tengen.

Kenjaku’s entire issue was not having enough cursed energy to do that all by himself. So he went around for centuries striking deals and making binding vows to get as much people to take part in the culling game.
He obviously promised them whatever their hearts desired but he honestly didn’t care much about them getting it or not. The end game was that everyone who participated would become good and enhance the amount of cursed energy accumulated from the culling game.

You could say the most important thing he needed to kick start the culling game was Mahito’s technique. Which allowed him to rewrite the Brains of those he had marked for the game . Some who were asleep (like tsumiki who ended up being a vessel) and others who he awakened techniques in (like higuruma).