Blood Moon

The Blood Moon is an event that has a small chance (1/7) of happening every night that is not a new moon. They will not occur unless at least one player has more than 6 hearts. It is heralded by the message "The Blood Moon is rising...".

During the Blood Moon

 * The store inventory of some NPCs change.
 * The spawn rate of monsters on the surface increases, and The Groom has a chance to spawn.
 * Zombies gain the ability to open doors after punching them several times (10 for one zombie). This can put the player's home and NPCs in peril, if they are not guarded appropriately.
 * Monsters will also spawn inside cities, despite the natural spawn protection they give.
 * All Bunnies and Goldfish will become corrupt.
 * Deathweed will bloom.

The benefits of a Blood Moon for more experienced players are the increased money and items they can harvest from the swarming Zombies and Demon Eyes, however it is advised that less experienced players should stay somewhere out of the reach of monsters during the event.

One way to survive a Blood Moon completely unharmed is to barricade all Wooden Doors by placing blocks beside them, as seen in the images below. A simpler way is to place all doors at least two tiles above ground, or dig a 2x2 trench in front of the door; zombies will jump to reach the door, and cannot attack the door while jumping. Or, make your entrance so high, that you have to double-jump before entering.

Another way to prevent your doors from being opened is to put an item (such as a torch) on the inside of the door. This prevents the door from opening inwards while still allowing you to exit and enter (to enter, you have to be facing away from the door, thus opening it outwards).

Hints

 * If the zombies are able to hit the door they won't leave. So if your doors are barricaded, this makes it really easy to kill them with the Vilethorn, Starfury, or Vile Powder.

Trivia

 * The Blood Moon's effect on monster spawns stacks with that of the Water Candle and Battle Potion.