Blood Moon

A Blood Moon is an event from The Legend of Zelda: Breath of the Wild. Hino is the first met character to explain the phenomenon. From 10:00 p.m. to midnight, based on in-game time, this event has a chance of occurring. The moon and the sky around turn red and the dark aura that is normally seen around Calamity Ganon will be everywhere. Its occurrence will cause all defeated enemies to revive from the dead.

During Link's first Blood Moon, Princess Zelda will telepathically warn Link of it and explains that Calamity Ganon's power increases during this time and tells him to be careful. She will also warn him each subsequent Blood Moon.

This is a point in time in which Calamity Ganon's power will rise to its' peak, hence the resurrection of foes that Link has already felled prior to this event. There are indeed positives to a Blood Moon, such as being able to collect items, parts, or weaponry from enemies that Link has felled without worry of said resources being limited, such as Bokoblin parts or Ancient Cores. Furthermore, Link will be told by Zelda during Blood Moon night if he decides to rest his head for the night either by campfire, sleeping in a bed, or sleeping at an inn or a stable.

If Link is inside a Shrine when the clock reaches midnight on a Blood Moon night, the Blood Moon will end without resurrecting any enemies and the cutscene is not triggered. This allows Link to avoid having enemies respawn until the next Blood Moon event.

Interestingly, cooking food on a Blood Moon night before the clock reaches midnight, produces better results as well. Link can ask Hino what Moon there will be that night, and during a Blood Moon night he will state "I'm getting that feeling again... Something is going to happen tonight. I can taste it."