The Blood Moon is an eerie mechanic in The Legend of Zelda: Breath of the Wild that enhances Ganon's power, allowing the spirits of fallen enemies to return to life by the red glow.

Be extra careful if you notice a red moon overhead (it is first possible to see it at 9:00PM or 21:00 in-game). You may want to avoid entering enemy camps or engaging Minibosses and bosses until after the Blood Moon passes at midnight. Enemies, including bosses, will regain all of their health after a Blood Moon!