A Blood Moon is a common randomly occurring event that takes place over the course of an entire night; however, a Blood Moon can also be initiated when the player uses a Bloody Tear. Blood Moons are signaled by the message "The Blood Moon is rising..." in the lower left corner of the screen (or the top middle of the screen on Mobile).
A Blood Moon will only occur if at least one player in the world has more than 120 life, and only on nights when a moon is present (any night except a new moon). Given those criteria, a Blood Moon has a
11.11*1/9 (11.11%) chance of occurring. It will also not spawn if another event is currently taking place, such as Lantern Night or Slime Rain. Weather-related occurrences (like Windy Days or Thunderstorms) do not count as events, so there can be crossovers.
While a Blood Moon is active, multiple effects can happen:
This content is transcluded from Blood Moon § Effects.
- The spawn rate of enemies on the surface increases. Dripplers, Blood Zombies, The Groom, The Bride, and the Clown (if in Hardmode) have a chance to spawn. Enemies not only spawn faster, but more are spawned than can normally exist on-screen at once. This works no matter the environment, so Corruption and Crimson enemies can also swarm even more than they normally would, for example.
- Enemies can even spawn near NPCs and their houses, whereas those usually suppress enemy spawns. Player-placed walls are not necessarily safe during this event.
- Zombies and their counterparts can open Doors.
- Goldfish become Corrupt Goldfish/Vicious Goldfish, Bunnies become Corrupt Bunnies/Vicious Bunnies, and Penguins become Corrupt Penguins/Vicious Penguins. Those spawned from Statues are Corrupt or Vicious , and they do not revert to regular Goldfish or Bunnies after the Blood Moon is over. If it is raining during the event, transformed Goldfish will flop around on the ground, rather than walk.
- The Merchant sells Throwing Knives.
- The Arms Dealer sells Silver Bullets (in Desktop version and Mobile version, only if silver is present in the world), and Tungsten Bullets if tungsten is present (Pre-Hardmode. In Hardmode, the Arms Dealer will always sell Silver or Tungsten Bullets ).
- The Clothier sells the Mime Mask, Fallen Tuxedo Shirt and Fallen Tuxedo Pants.
- The Dryad stops selling Purification Powder, Sunflowers, and Grass Seeds.
- If the world was created with the Corruption (or she is in a Graveyard in Hardmode), she will sell Vile Powder and Corrupt Seeds.
- If the world was created with the Crimson (or she is in a Graveyard in Hardmode), she will sell Vicious Powder and Crimson Seeds.
- On the Old-gen console version and version, she will also sell Sparkly Wings during Hardmode.
- The Painter sells the Evil Presence painting.
- The Dye Trader sells Bloodbath Dye.
- The Steampunker sells Purple Solution if the Corruption is present, or Red Solution if the Crimson is present instead of Green Solution.
- The Cyborg sells Rocket II ammunition.
- The Skeleton Merchant sells the Slap Hand during Hardmode.
- Deathweed blooms. Blood moons (and Full Moons on Desktop, Console, and Mobile) are the only times you can harvest Deathweed Seeds from Deathweed (with the exception of harvesting with a Staff of Regrowth).
- Most NPCs have their own unique lines commenting on the event.
- The Zoologist NPC will transform into her werefox form regardless of the moon phase.
- Fishing power is 1.1x stronger, and can provide some unique items and spawn unique enemies, including the Dreadnautilus.
- Visual effects:
- Almost all water will turn red, including Rain. Exception: The Ocean will not turn completely red, though it will be affected by the screen filter.
- A red filter will be applied to the screen as well, shifting the colors of all entities and light towards red and purple shades.
- This will also affect the projectile colors of many weapons.
- Placed Living Cursed Fire Blocks turn yellow, making a unique effect.
- The Glowing Mushroom Biome, which is normally blue, will have the red shader make it appear pink-purple.
While a Blood Moon can be dangerous to new players, it can also wield great rewards.
- The Groom can drop the Top Hat, and when killed for the first time, will give the Till Death achievement.
- In Hardmode, enemies can drop the KO Cannon.
- In Hardmode, more enemies can be fished and can give more Blood Moon exclusive items
- Enemies exclusive to the Blood Moon can drop the Bloody Tear.
- Enemies caught during fishing can drop the Chum Bucket ,an item that increases fishing power. Other fishing drops include the Vampire Frog Staff, the Blood Rain Bow, and the Advanced Combat Techniques, an item that permanently increases NPC's Attack and Defense.
- Dripplers and Blood Zombies can drop the Shark Tooth Necklace, a decent early-game accessory and the Money Trough, an item that lets you access your Piggy Bank anytime, anywhere.
This content is transcluded from Guide:Practical tips § Combat.
- For nocturnal bosses, starting the battle just after the sun sets (7:30 PM) will provide the maximum amount of time to defeat the boss. In Hardmode, the Moon Charm and/or Moon Stone and their upgrades are also useful at night.
- Boss battles can be won or lost before the battle ever starts. Choose your equipment and have it ready; find and/or make potions and placed buffs; use the highest-tier food you have available; set up an arena appropriate to the boss; learn the strategies for the boss you're facing.
- Prepare your Boss-fighting arena with adequate lighting, Campfires and Heart Lanterns for health regeneration, and Stars in Bottles for mana regeneration if you use magic. Bast Statues will provide a significant defensive boost. Garden Gnomes and (if underground) proper torch placement will reduce damage taken and increase damage dealt due to the luck. Note Torch God's Favor helps with this. Honey pools can also be used for extra health regeneration.
- Sunflowers provide the Happy! buff to players within a 50-tile radius, which grants a +10% movement speed bonus and 17% reduction in enemy spawn rate.
- Always carry around one stack of the highest-tier healing potion available (Lesser, Normal, Greater, or Super Healing Potions). Relying only on natural Health Regeneration is not a good idea.
- It is suggested to build houses for the Dryad and the Nurse NPCs in your arena. The former casts the Dryad's Blessing buff, which increases your defense and provides you with a thorns-like effect, while the latter can heal and remove debuffs instantly, at the cost of some coins.
- Bosses are displayed on the Minimap: Follow the boss's icon to track it when you're struggling to find it. You can identify the boss icons by checking their respective wiki pages.
- Once you have freed the Mechanic in the Dungeon, you can use Wire to enhance your arena with Traps and helpful Heart and Star Statues. The former helps to damage the enemies, though be careful to set them up correctly in order not to hurt yourself during the battle. The latter will spawn heart and star pickups, respectively. Connect these devices to timers.
- It may be useful to summon and kill the Eye of Cthulhu or King Slime before summoning any harder boss in order to spawn an extra one-use pool of Hearts. Note that this will prevent any Heart Statues from spawning new Hearts.
- Remember to use the Sharpening Station, Ammo Box, Crystal Ball, Bewitching Table, and Slice of Cake before you go to explore or battle bosses/invasions. These will give boosts that are useful to take, with the first four being class-specific. They give Sharpened, Ammo Box, Clairvoyance, Bewitched, and Sugar Rush, respectively.
Due to the NPCs being vulnerable to enemies during this event, it is recommended that you make your base in the sky at the beginning. If you have already made a base, a simple barricade of a block behind a door will prevent most enemies from getting in. You will want to move your base above ground level before Hardmode, as the increased enemy spawn rate will result in more Wraiths spawning, which can be a nuisance; however, they can only move upward if they're inside a block. A simple ditch can take care of most ground level mobs, even Clowns in hardmode. Even better, line the bottom of the ditch with lava and it will kill them for you. You will want to place a thin layer of lava in the ditch, enough to burn Copper Coins, but not silver ones. To make sure that the amount of lava is correct, throw a copper coin in. If it burns, you have met the minimum requirement. If not, add more until it does, but slowly until the coin disappears. Next, throw a silver coin in. It shouldn't burn. If it does, remove some and try again. Repeat until the copper coin burns, but not the silver. As said above, traps can make the arena even deadlier when used correctly. Keep in mind that Drippers can hover and fly above your defenses.
Also, if you do not want to build an arena, you can use weapons that attack through blocks (for example, the Vilethorn pre-Hardmode, or a Crystal Vile Shard or Life Drain in hardmode) to attack mobs while being safe in your house. If you have defeated Plantera, you can use the Nettle Burst. You can do this by blocking your doors with blocks or having a base that is high off the ground, while using a weapon (like the ones suggested above) to attack the enemies that come. If you have a floating base, you can put a lava pit underneath your base as well.