The Blood Moon is an event in Terraria.
A Blood Moon happens at nightfall (7:30 PM) during any moon phase except for the New Moon and will continue until dawn. The Blood Moon is always heralded by a message saying "The Blood Moon is rising... ", which will appear in the bottom-left corner, and, rather than the regular night music, the "Eerie" song will begin playing.
Each night has a 1/9 (11.11%) chance of the Blood Moon rising when at least one of the players in the world has at least 120 health, or six hearts. The event can occur in any mode, making it very dangerous to beginning players, especially in Expert Mode.
As the night progresses, the moon and sky will become progressively more red, an effect which peaks at midnight. The above-ground world will also be tinted reddish-pink, and the water and Rain will also change to red (added in 1.2).
During a Blood Moon, enemy spawn rates on the surface double, the ability of NPCs to reduce the spawn rate of nearby enemies is temporarily disabled, and the maximum number of enemies able to be spawned at once increases. It also becomes more difficult to keep NPCs safe, as Zombies gain the ability to open doors and Goldfish, Bunnies, and Penguins will turn corrupt. Do take note that the Blood Moon will not affect underground enemies.
Some Blood Moon exclusive mobs include The Groom, along with Clowns in Hardmode. On the PC Version, The Bride, Blood Zombies, Dripplers, and the Crimson versions of the Corrupt Bunnies, Goldfish, and Penguins will spawn.
Because the requirements of a Blood Moon are so low, most new players end up experiencing a Blood Moon soon after they use their first Heart Crystal. To prevent the deaths of you and your NPC's, it is advised that players with less than 200 health or 11 defense should go underground for the night. This is the simplest and easiest defense, because there are no Blood Moon mobs that spawn underground.
If you do not want to risk going underground or fighting, you will want to hole up in your house. To stop Zombies from entering your home, dig a 2x2 trench in front of your door or doors.
Another way is to place a solid background object (ie. a Wood Platform or torches) on the inside of a door, so that the door cannot open inwards. This way, you can open the door to leave the house easily enough, but Zombies will not be able to open it no matter how much they bang on it (NPCs can still use the doors effectively).
If you have access to a Mechanic, then you can simply use Active/Inactive Stone Blocks as your door. However, this does not count as a door for NPC houses, and if left open/inactive for too long, the NPC living there will leave. You can also use activators as doors, which will allow you to match the blocks that your house is made of. This is effective because no other mobs can pass through with the exception of mobs that can pass through blocks.
The most effective way of blocking out zombies and other earth-bound monsters is to simply build your NPCs' houses suspended in the air (at least 10 blocks above the ground is recommended). If you do this, no further protection is necessary, as the enemies which can open doors or do not need doors cannot reach you, and the enemies which can reach you cannot open doors.
Due to the increased rate of enemy spawning, fighting monsters on a Blood Moon is a great source of income, Lenses, and other materials. If you choose to fight on a Blood Moon, Silver Armor or better is recommended.
Players who do not want to fight, but want to collect drops from monsters on Blood Moons can do so by building a lava trap:
- 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 test the pit, step in the lava. If damaged, the pit will function defensively.
- Throw an item in the pit. If the item is not destroyed, the pit is perfect.
Another effective lava trap is to dig a pit ten blocks long and at least two blocks deep. Make a box out of solid blocks over the center of the pit; it should be 5 blocks tall and 4 wide, with the inside top blocks covered with platforms. In the pit, add a single lava bucket and let it spread out. If the pit is exactly 10 blocks wide, the lava will be deep enough to damage but not to destroy items.
- A Blood Moon is the only time period that Deathweed will bloom and drop seeds.
- Occasionally, some NPCs will sell items that are only normally purchasable on a Blood Moon during the daytime. This means that the night is going to be a Blood Moon.
- It's possible to have a Blood Moon at the same time as a Full Moon. On Hard Mode worlds, this usually causes a swarm of Werewolves, which allows you to effectively farm the Moon Charm.
- It's possible (albeit rare) to have multiple Blood Moons in a row, due to the equal chances of it happening every night.
- Corrupt Bunnies can be farmed much more easily during a Blood Moon.
- The New Moon moon phase is the only phase in which it is impossible for a Blood Moon to happen, due to the fact that there is no moon to be a Blood Moon.
During a Blood Moon, NPCs will display unique dialog. Female NPCs (Except for the Party Girl) appear to be in a bad mood 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."
- "Hey, buddy, do you know where any deathweed is? Oh, no reason; just wondering, is all."
- "If you were to look up right now, you'd see that the moon is red."
- "Am I about to DIE!?"
- "Hey, this house is secure, right? Right? <Player Name>?"
- "Not even a Blood Moon can stop capitalism. Let's do some business."
- "Keep your eye on the prize, buy a lens!"
- "Oh great, I can hear [Name of Mechanic] and [Name of Nurse] arguing from here. (only if Mechanic and Nurse are present.)
- "I've got something for those zombies, alright!"
- "There was a bomb sitting right here, now I can't seem to find it..."
- "Hey, have you seen a Clown around?" (Clowns only appear during Hardmode Blood Moons, but the Demolitionist says this during any Blood Moon.
- "Dude, is it just me or is there like a million zombies out tonight?"
- "I sell what I want, alright! If you don't like it, too bad."
- "I don't want you to buy my stuff, I want you to want to buy my stuff, ok?"
- "Why do you have to be so confrontational during a time like this?"
- Arms Dealer
- "I love nights like tonight. There's never a shortage of things to kill!"
- "Man, it's a good night not to talk to anybody, don't you think, <Player Name>?"
- "... We have a problem! It's a Blood Moon out there!"
- "Hurry up and stop bleeding."
- "What's that supposed to mean?!"
- "I don't think I like your tone."
- "Oh, let me guess. Didn't buy enough wire. Idiot."
- "I don't appreciate the way you're looking at me. I am WORKING right now."
- "Just-could you just..Please? Ok? Ok. Ugh."
- "All I want is for the switch to make the... What?!"
- "Tipping IS optional, but remember I have access to scissors and your head."
- "This is a cut-throat razor by the way."
- "You better stay outta my hair tonight, hun. I just sharpened my scissors, and i'm looking for an excuse to use them!"
During a Blood Moon, NPCs will also sell different items:
- Dryad will sell Vile Powder, Corrupt Seeds, and the Sparkly Wings ( and Hardmode only)
- Merchant will sell Throwing Knives
- Arms Dealer will sell Silver Bullets.
- Clothier will sell the Mime Mask.
- Painter will sell the Evil Presence.
- Steampunker will sell the Purple Solution or Red Solution depending on your world.
- As of update 1.1, the Blood Moon has been given a more noticeable effect on friendly NPCs as well, primarily the female ones. Quotes from the Nurse, Dryad, Stylist and Mechanic all seem to show hostility or annoyance and even bad stress when acknowledging the player, compared to other days/nights. This is possibly a joke using "Blood Moon" as a reference to females' menstrual cycles.
- The Blood Moon event may be based on a real world event, known as a Lunar Eclipse. During the eclipse, the Moon can sometimes gain a reddish tint to it. This also goes hand-in-hand with both the real life and other Terraria event, known as a Solar Eclipse.
- The Blood Moon also may be based on one of the "Seven Signs of the Apocalypse" from the Bible, in which it states that ,"...on the 6th sign the moon will arise, showing the color of blood, bringing with it the demons that prowled the Earth, but were sealed away. Then they will feast on those who doubted...".
- When the Blood Moon rises, your pet worm (if you summoned it) will shout, "Incoming!"
- The "Eerie" song soundtrack that plays during a Blood Moon is also used in the close vicinity of a Meteorite.
- Rain now turns blood-red during a Blood Moon.
- Water now turns blood-red during a Blood Moon.
- The chance of a Blood Moon occurring on a random night was decreased from 1/7 to 1/9.
- Added to the game.