The Blood Moon is an event that has a 1 in 10 chance of happening every night as long as one player in the world has 120 health or more. A message saying: "The Blood Moon is rising..." is displayed when the event starts. During this event the spawn rate of enemies and the maximum amount of enemies that can be on the screen at any time is increased. Enemies will also spawn near NPCs, even when they normally do not.
During a Blood Moon, Zombies, Werewolves and Possessed Armor can open doors after a few hits.
Special enemies spawn in addition to the usual enemies of the surface biome the players stands in. The following enemies spawn only during a bloodmoon: