Blood Moon

The Blood Moon is an occasional event in Terraria which causes the moon and the sky to turn red. During a Blood Moon, enemy spawn rates double, Zombies can open doors, and Goldfish/Bunnies turn corrupt, exposing any NPCs in the path of the monsters to harm. Each night has a 1/9 chance of the Blood Moon rising. Because of these effects, it would be a good idea to barricade your house by making no way in for monsters if you are just starting out.

As of 1.1, the following creatures have been known to attack without meeting other requirements: Werewolves, Wyverns, Unicorns.

When Night comes and it's a Blood Moon, a message will appear saying "The Blood Moon is Rising...". Fighting monsters on a Blood Moon is a great source of income, due to the increased rate of enemy spawning. You will most likely do very well if your character has at least medium-level equipment (Silver is usually very good during Blood Moon attacks, although if your house has only one entrance it is possible to use lower level). Others who are not so fortunate and wish to survive may wish to block Doors and seal off entranceways. If a 2x2 trench is dug in front of a door, Zombies are unable to open it because they cannot knock and jump simultaniously.

The easiest and most effective way of blocking out zombies and other earth-bound monsters is to simply build your NPCs' houses suspended in the air. A gap at least 10 blocks high should work. You can make a workshop underneath the houses as well! This technique works very well if you just can't be bothered to protect your house (The Blood Moon does drag along a bit).

Another way to block out Zombies is to place a solid object in the way of the door opposite the outside.

You can open the door one way as much as you want (you can open it both ways, but you have to be facing a different way each time you do it), but Zombies will not be able to open it the opposite way. NPCs can still use the doors effectively.

There is also a trick where you can put one block in front of the door and open it while the Zombies are outside. Since Zombies follow the Fighter AI, when they realize they can't get to you, they will retreat and despawn. Although this doesn't give you any loot, it's a quicker way to get rid of Zombies.

Of course, if you have fairly powerful weaponry and armor, you can simply let the Zombies and Demon Eye into your home, where you can group them up and kill them. Doing so is a good way to acquire money and materials like lens, which can also be sold for some small funds.

Players can additionally create lava pits to farm for coins. Build a pit for the player to stand in and on top of. Place a roof that also is a pit 1 block thick. Fill it with 1 bucket of lava. Since monsters always try to reach the player, they will touch the lava and die. To make sure this works, step in the lava with health potions. If damaged, the pit works. Next, throw an item in the pit. If the item is still regainable, the pit is perfect.



A Blood Moon is the only time period that Deathweed will drop seeds.

During a Blood Moon, NPCs will also display unique dialog. Here's a list of quotes that can only be seen during a Blood Moon.


 * "You can tell a Blood Moon is out when the sky turns red. There's something about it that causes monsters to swarm." - Guide


 * "Keep your eye on the prize, buy a lens!" - Merchant
 * "Hey, this house is secure, right? Right? [Player Name]?" - Merchant
 * "Not even a Blood Moon can stop capitalism. Let's do some business." - Merchant


 * "I've got something for those zombies, alright!" - Demolitionist


 * "Dude, is it just me or is there like a million zombies out tonight?" - Dryad
 * "I sell what I want, alright! If you dont like it, too bad." - Dryad
 * "I don't want you to buy my stuff, I want you to want to buy my stuff, ok?" - Dryad
 * "Why do you have to be so confrontational during a time like this?" - Dryad


 * "I love nights like tonight. There's never a shortage of things to kill!" - Arms Dealer
 * "Man,it's a good night not to talk to anybody,don't you think,[Player Name?]" - Arms Dealer

During a Blood Moon, NPCs will also sell different items:
 * "[Player Name]... We have a problem! It's a Blood Moon out there!" - Clothier
 * "WHAT!?" - Nurse
 * "Hurry up and stop bleeding."-Nurse
 * "What's that supposed to mean?!" - Nurse


 * The Dryad will sell Vile Powder and Corrupt Seeds.
 * The Merchant will sell Throwing Knives and Glowsticks.
 * The Arms Dealer will sell Silver Bullets.
 * The Clothier will sell the Mime Mask.

Trivia

 * The Blood Moon may be a reference to the game The Elder Scrolls III: Morrowind Bloodmoon expansion, in which at the end of each era the moon turns red and the Daedric Prince Hircine manifests to hunt with his minions, also hinting with the increased spawn of werewolves.
 * A Blood Moon can only appear if one Player has 6+ hearts (120+ HP).
 * Unless the player has beaten the Wall Of Flesh, the arms dealer will only say "Hey, I heard there's a doll that looks very similar to (Guide's Name) somewhere in the underworld. I'd like to put a few rounds into that."
 * As of update 1.1, the Blood Moon has been given a more noticeable effect on friendly NPC's as well, primarily the female ones. Quotes from the Nurse, Dryad and Mechanic all seem to show hostility or annoyance and even bad stress when acknowledging the player, compared to other days/nights. This may simply be fear or unease though. Or the Blood Moon being a reference to "that time of the month." Male Vendor NPC's show excitement for the Blood Moon, as it may increase their sales.
 * As of 1.1, during a Blood Moon, the Possessed Armor enemy has the ability to open doors.
 * As of 1.1, during a Blood Moon, Zombies have the ability to knock down doors.
 * As of 1.1, the chance of a Blood Moon was increased to 1/9 from 1/7 in earlier versions and a 2/7 chance on a full moon on both modes
 * It is rare, but possible to have a Blood Moon at the same time with a Full Moon, usually causing a swarm of werewolves to appear on hardmode worlds, allowing you to effectively farm the Moon Charm.