The Moon Lord is the final boss of the Celestial Event, and is also implemented as the final boss and main antagonist of Terraria. To summon the Moon Lord, the four Celestial Pillars must be defeated (Nebula, Solar, Stardust, Vortex). After the final pillar is destroyed, the message "Impending doom approaches..." appears at the bottom left of the screen. The screen will then begin to vibrate periodically with fading vision. Any background music that is currently playing is also dimmed. After about a minute, a white flash will appear unveiling the Moon Lord. Anything in the foreground (other than the Moon Lord) is darkened and starts blurring, while the background is completely darkened until the fight ends. Note that it will not leave until the player wins or dies, even when teleporting long distances. Defeating the Moon Lord rewards the player with the "Champion of Terraria" achievement, and if all other bosses have been beaten already, you will get the "Slayer of Worlds" achievement. He also drops a random weapon from the relevant pool, plus some Luminite used for the crafting of endgame items and armor.
The boss has 3 sections (2 hands and the head) that must be killed by attacking the eyes in the center before its core is exposed. Killing the core will defeat the boss. The eyes can only be damaged when they are opened, and they only open when attacking.
The central head eye (45000 HP) will open only occasionally to unleash a very powerful Phantasmal Death Ray that will sweep partly across the screen in the player's direction, doing massive damage. After the beam finishes, the eye will shoot several homing projectiles before closing again.
The eyes on both hands (25000 HP each) will be open most of the time as they are regularly churning out attacks. They will release homing missiles that chase after the player that does moderate damage. They will also summon large, invulnerable eyeballs and fling them at the player, doing moderate damage.
When an eye socket runs out of health, the eye will leave the hand/head as an indestructible True Eye of Cthulhu. The True Eye will hover around the Moon Lord, releasing a variety of attacks that do moderate to high damage. All True Eyes of Cthulhu are identical, regardless of whether they spawned from the hand or head. Only when 3 True Eyes of Cthulhu are present will the 50000 HP Core be exposed and vulnerable.
Throughout the fight, the Moon Lord will regularly extend a "tongue" that latches onto nearby players. It will then drain the player's life (the player does not lose health from this) in the form of white particles (Moon Leech Clots) that travel along the tongue. The particles are destructible and if a particle successfully reaches the Moon Lord, one of its body parts (any that have not been defeated yet) will regain 1000 HP. The Moon Lord will drain 3 particles before stopping. The tongue will not go through blocks, and the mouth will always be positioned above the player so that it can extend the tongue, even resorting to being directly behind the player if they are in a 2 by 3 space. If there are no blocks above the player, the mouth will always attempt to be about 10 blocks above them. As of 18.104.22.168, the Moon Lord will place the Moon Bite debuff on players when leeching them, causing them to be unable to regain health from weapons, such as from Vampire Knives or the life steal of the spectre armor.
Note: it's not advised to fight the Moon Lord on multiplayer, as the tongue will drain life from everyone who's fighting it. If the health particles aren't focused on, the Moon Lord will regenerate 24000 hp (on 8 player MP) and it can stack on top of health it already has, so within 5 attack cycles it will have gained 120000 hp.
It is usually a good idea to destroy the central head eye first. Firstly, the phantasm beam attack it uses can do over 100 damage even with high armor, although it can be dodged. Secondly, in general, the attacks from the True Eyes of Cthulhu are more dangerous than if they were left as the hands, as they do higher damage. It can be very difficult to survive both the attacks from the True Eyes while dodging the Phantasm Beam. Hence, destroying the hands before the head can leave players in a difficult situation.
Destroying the leeching particles should also be a top-priority as the boss can heal at a very fast pace with them. They are relatively easy to destroy.
If a player can obtain a mount from a Cosmic Car Key or a Shrimpy Truffle before the boss fight, it can make the fight much easier due to the unlimited flight they provide. Note that Shrimpy Truffle is expert mode exclusive. By default, the UFO flies faster.
If the player uses Shrimpy Truffle (Cute Fishron), it is recommended to buy some bubble blocks from the Party Girl NPC and place bubbles filled with water or honey in particular areas of an arena, as it gives a lingering boost for the Cute Fishron mount when in contact with water.
It is possible to obtain a higher speed than the Moon Lord itself, allowing players to kite it around the map while staying out of range of some of its attacks while pelting it with ranged weapons (tested with Beetle Armor, Spectre Wings, Frostspark Boots and a Cosmic Car Key). This can be done simply using the UFO Mount, because its top speed is slightly faster than Moon Lord.
If playing multiplayer have the host set their frame skip to subtle and stand near the nurse, because of the immense lag the Moon Lord can land very few hits and can't use the beam since to be with the nurse the host must be in her home. As the host takes damage, have him heal at the nurse since he can't easily die all the other players can dispatch him with as many deaths as they need.
Melee classes can be difficult to use against the Moon Lord, as the eyes generally stay out of the player's reach. However, melee weapons with a long range (such as spears) or shoot projectiles (like the Influx Waver) can serve as a good weapon. The Solar Eruption is the most effective melee weapon that is also easily obtainable before the Moon Lord fight, taking 18 Solar Fragments to craft with Solar Pillars dropping 25 at a minimum. It has a very high damage-per-second and can be used from behind cover since it pierces through walls. This lets you avoid most of the Moon Lord's attacks while still being able to damage him heavily in return.
Another strategy is to be in an NPC house that contains the nurse, grapple to the ceiling to make yourself invincible to knockback and aim the Solar Eruption at the Moon Lord's main eye and then use a sword that shoots projectiles (they hit the hands much more often) and aim out the door to take care of the hands and finish the core with the Solar Eruption.
The simplest melee strategy only requires the Solar Eruption, a bit of honey, a heart lantern and solid blocks needed to encase the player for protection from Moon Lord's several types of lasers.
If your aim is accurate enough with projectiles, you can use the Daybreak to deal large amounts of damage to the Moon Lord without taking too much damage. If said strategy is used, make an arena in a similar fashion to a bunch of rows of platforms being 400 blocks long and a distance of 20 blocks from each other.
This strategy is possibly the easiest but requires a great deal of preparation and patience, and several stacks of Chlorophyte Bullets. A Mechanical Cart is also strongly recommended, and essential when employing this strategy in Expert Mode. Armor should be Beetle Armor (with the Beetle Shell), or if Moon Lord has been beaten a few times already, the Solar Flare Armor, or Vortex Armor. Shroomite is acceptable if not in Expert mode. Chain Gun, Megashark, or Vortex Beater are the weapons of choice. If the player doesn't have enough Chlorophyte ammunition, make Crystal Bullets (area damage) or the most damaging bullets possible.
Another strategy is to use Phantasm with Holy Arrows. Since Phantasm creates trails once it's fired and locked to an enemy, it will make higher DPS. For easier dodging, wear Master Ninja Gear and ride UFO Mount using Cosmic Car Key.
Accessories should all be forged to Warding. Bonuses to speed do not affect Minecart travel.
To set up the Arena, make an above-ground cart track that runs at least two full-screen lengths. The longer this track is, the better. At each end, create a "bumper" ending with a hammer. Then, go along the track and place platforms at eye level. This will serve as a platform for all of the Heart Statues, Star Statues, Campfires, and buff givers. The more statues the better. Wire the statues up to a 3 Second Timer or better.
Optionally, there can be a row of blocks periodically above the track to serve as cover from the Moon Lord's beam attack, so long as there is a way to attack him back. Another variant is to use Pressure Plate Track with Teleporters to create a multi-level track arena to dodge in and out of cover, or at each end of the track to keep the movement direction constant.
The fight will consist of running away at top speed in the minecart and shooting backward and upward as the Moon Lord tries to catch up. When the cart hits the bumpers on the end of the track, the cart continues at the same speed in the other direction, freeing the player to concentrate on DPS and their own health. Using Chlorophyte ammunition gets the best results, as the Mechanical Cart travels 102mph at top speed, and the Moon Lord will teleport in largely off-screen behind the player. This method can take a long time, but as the player will stay out of range of most enemy attacks and only occasionally need to heal when hit by the eyebeam, it is one of the easiest.
Fight, Warp, Nurse, Repeat.
First, you need to make sure your Nurse is near your spawn point. Then you do everything as normal, keeping the Moon Lord away from your spawn point, and only teleporting back if you can't use a potion and need to heal badly (for example, having 100 health and no potions). Unlike the majority of bosses, Moon Lord does not despawn unless all players are dead, therefore, you can go very far away for fighting purposes then warp home to heal.
If you're in normal mode, you should teleport when you reach 200 or 250 health. In expert mode, that can up to 300 hp. If you don't have the Potion Sickness debuff, drink one first, and then teleport. The Nurse will not remove potion sickness, so act fast.
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Multiplayer "juggle" strategy
this strategy can be done with any class as long as you have 2 players that can reach over 1000 DPS. defense doesn't really matter but can be extremely helpful with the phantasmal deathray and other weapons. You let a player handle the attacks and wait until he teleports to you when the other player dies. then you unleash your full force on the Moon Lord and not die until the other player respawns. then after you die, you let the other player have it and stay out of the moon bite range. you need lots of mobility for this strategy and endurance.
Dissonance Hook Strategy
you need a lot of hook experience for this strategy. you need an arena made mostly out of platforms, a dissonance hook, and weapons of your own. you need a lot of hook experience to avoid all his attacks. you hook behind, or out of the way of his attacks and any weapon you can use can be effective.
Old One's Army Gear
Gear from the Old One's Army can be very effective in dispatching the pillars before facing the Moon Lord, specifically, the very high defense Valhalla Knight Armor and armor ignoring Ballista Staff. The heavy defense of the armor is higher than any of the armor sets from the pillars except for the Solar Flare Armor (which also require the Moon Lord to have been defeated to craft with Luminite Bars) which will allow you to take more punishment, and the set bonus will also amplify any summons, and speed up the fire rate of the Ballista Staff when getting injured. This allows the player to more easily farm the pillars and obtain better gear, such as the Daybreak which stacks damage over time, and placing Ballista Staff sentries on a flat area when the Moon Lord spawns allows decent damage to his exposed body parts.
In addition, the Valhalla Knight Armor has an incredibly high health regeneration effect which applies even if the player is affected by Moon Bite, the debuff by the Moon Lord which stops health regeneration effects. This allows a decent amount of tanking which helps players who aren't well equipped for the fight.
To set up an arena based on this setup, all that is required is a few lines of solid blocks to block some of his ranged attacks and his main beam, while still allowing the player to exit the arena to stack Daybreak spears on the exposed 'eyes'. Create a single line of solid blocks to stand on about 20-30 blocks long out of Asphalt, as this will be your main way of moving back and forth to dodge any attacks that can go through blocks. Next, erect short 1 block thick pillars of any material at the ends of this path about 5 or 6 blocks high, to block some of the attacks from his hands and some of the True Eyes Of Cthulhu. Now erect another line of Asphalt 5-7 blocks above these pillars, leaving the 5-7 gap toward the top or bottom to allow yourself to get out of the arena quickly if necessary. This top line of blocks will block the Moon Lords beam entirely while in the box, and can be used to set up the aforementioned Ballista Staff sentries on top, 4 in total with the Valhalla Knight armor bonus, which will fire slow-moving shots that will add extra damage as you dodge. If you get hit by any attack the sentries will fire more rapidly, only helping you in the long run, with the regenerative effects of the armor quickly regaining this lost health. Simply use the Daybreak and fire through the gaps on the walls at his hands, stacking damage until they have been dispatched.
Once the Moon Lord's hands have been dispatched, the fight gets more difficult. You must now dispatch his eye on his head which your Ballista Sentries should have weakened slightly already, by jumping out of the arena and onto the top part, exposing yourself but allowing yourself to aim the Daybreak at his center eye right before he charges it up, then quickly heading back down into the box when he fires. Simply rinse and repeat this while re-placing your Ballista Sentries when they expire, until his heart-core becomes exposed. Now stand up on the top path you have made and use the asphalt to run back and forth while firing the Daybreak at it, OR use wings or flying Mounts to dodge his attacks as you weaken his core.
After defeating the Moon Lord and obtaining either the Lunar Portal Staff or Rainbow Crystal Staff, the fight can be further enhanced by using these in place of the Ballista Sentries, forgoing the armor ignoring effects with faster attacking sentries, which can still be stacked up to 4 times with the Valhalla Knight Armor, which makes further Pillar and Moon Lord fights more manageable.
- This boss is extremely difficult, and preparations are crucial. It is a good idea to craft the weapons made from the pillar fragments and to wear the highest armor possible.
- Melee sets are not as disadvantaged as you'd expect, as the Solar Eruption can be one of the most powerful weapons against his hands and eyes thanks to it's long range and the ability to ignore walls, as well as the Possessed Hatchet if you don't want to aim.
- This battle, depending on your class, may be easier or harder than both Plantera and the Lunatic Cultist.
- Upon dying, the Cultists will respawn and you will have to defeat the Lunatic Cultist, as well as the 4 Pillars (unless you craft a Celestial Sigil), so it is recommended that you back-up your world before fighting the final pillar. This can, however, be useful as it allows the player to farm fragments pre-Moon Lord if they don't have enough to make all the lunar weapons to ease up the first fight.
- If you quit for any reason after the final pillar has been destroyed, Moon Lord will not spawn and you will need to defeat the Lunatic Cultist as well as all four pillars all over again without Celestial Sigil. However, this allows farming the fragments as Celestial Sigil is only useful if the player has a huge amount of fragments but wants a lot more luminite.
- If you kill the head during its death-ray attack, the beam won't be stopped and will continue to exist, even though there is seemingly no source of it.
- You can easily dodge the Phantasmal Beam attack by using Rod of Discord. But don't abuse it, since it has a cooldown and if you use it while the Chaos State debuff is in place, you will take damage equal to 1/6 of max health.
- This boss bears resemblance to Cthulhu, the deity created by H. P. Lovecraft. This is due to fan speculation prior to update 1.3 that Cthulhu itself would be the final boss of the game (hence the bosses Eye of Cthulhu and Brain of Cthulhu). Cenx later confirmed that the Moon Lord actually represents Cthulhu's brother. (He may be Hastur, Cthulhu's half-brother in Eldritch mythology.)
- The Moon Lord's brain appears to be a Brain of Cthulhu similarly colored to Ocram from the console and mobile version.
- The Moon Lord's color scheme is identical to the Vortex Pillar and the enemies it summons.
- Originally, the final boss of Terraria would've been the moon itself descending upon the world, but this was scrapped, probably due to being extremely similar to the Moon in The Legend of Zelda: Majora's Mask.
- The Moon Lord's name is "Steve" confirmed by Re-Logic. 
- Even though he is the final boss, Moon Lord is only immune to confusion and does not drop a lot of money.
- This is shared with Duke Fishron as it only drops 1 gold despite being a Hardmode Boss.
- However, Moon Lord and Duke Fishron both compensates that with their better loot quality.
- Once his core is out of health, he will remain for ~10 seconds, causing many cosmetic explosions on-screen. After that, he will explode one final time and the only things left behind are his skull and ribcage that disappears a few seconds later.
- If all players are dead when this happens, he will disappear and drop no loot.
- Moon Lord can be summoned in any world where the Golem has been defeated once.
The Moon Lord’s phantasmal deathray can now go through blocks to attack the player.
The Moon Lord's attacks now cause their own separate invincibility frames on impact with a player. v126.96.36.199
- Can now be summoned using a Celestial Sigil.
- Added to the game.