- 1 Spawn Condition
- 2 The Fight
- 3 General Strategies
- 4 Specific Strategies
The Twins can be spawned by fulfilling either of these conditions:
- Smash a Demon / Crimson Altar. They will then have a 10% chance of appearing when night falls. Note that this condition is shared with the rest of the mechanical bosses, which increases as more of the three are defeated. This method will only work if The Twins have yet to be defeated;
- Use a Mechanical Eye during Hardmode at night.
The Twins must be killed before dawn (4:30 a.m.), otherwise they flee and despawn.
The Twins, as the name suggests, are two separate monsters, both of which must be defeated. They have a combined health of 43,000 / 64,500, shared between them. Retinazer is distinguished by its red iris and lasers, while Spazmatism can be identified by its green iris and cursed flames projectile.
When an Eye is reduced to 40% of their maximum health, it will transform, gaining a slight boost in offense and defense. Each Eye transforms independently once reduced to 8,000 / 12,000 HP (Retinazer) / 9,200 / 13,800 HP (Spazmatism); the other eye remains in its original form until it is reduced to the appropriate amount. When one is destroyed, the other will continue attacking in the same pattern.
It is a good idea to focus on one eye, since the fight becomes easier if a single eye has been defeated. Additionally, the fight becomes considerably harder if both eyes are on their second form.
In its first form, Retinazer will fire lasers at the player at a steady but somewhat slow rate. This is occasionally interrupted by charging attacks, which mirror that of its partner. Retinazer does slightly less damage than Spazmatism, but this is offset by its higher accuracy thanks to the speed of the lasers. When not charging, Retinazer will always be aligned diagonally with the player, positioned above them.
When it changes into its second form, it will no longer engage in charge attacks. Instead, its lasers will progressively fire at a faster rate as it loses health. This is occasionally supplemented by a weaker but much more rapid laser attack that tracks extremely well. To avoid this, try to fall as fast as you can, and you can be left unscathed. With wings it is possible to "zig-zag" up and down to dodge the lasers. This is made trickier as the fight goes on, with Retinazer using quicker lasers that are much harder to dodge.
Spazmatism, like Retinazer, alternates between firing Cursed Flames from a distance and engaging in charging attacks. The flames do more damage than the lasers, but are not as fast and thus easier to dodge. However, the Cursed Inferno debuff can be very dangerous for its high damage over time and its ability to stop health regeneration. Its charge attacks are faster and more agressive than Retinazer.
Spazmatism's second form changes its attack pattern dramatically. Its Cursed Flame attack becomes a constant stream of flame, which will last for several seconds (and deal large amounts of damage). However, it does not chase the player as quickly as it does in its first form, making avoiding the attack somewhat easier. Once it stops spewing flame, it will charge with greatly increased speed, which also does a lot more damage. Much like Retinazer, it is a good idea to fall as fast as you can while it is charging, and you should be okay. Redirecting Spazmatism's charges is easier than it sounds; if you jump as he slows down, he will charge over you. This causes Spazmatism to charge at you from either above or below, making him easier to dodge if you just run.
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 a stack of the highest-tier healing potion available, as relying only on natural Health Regeneration is not a good idea. Depending on the game stage, this can include items such as Mushrooms or Honeyfins. On the Desktop, Console, Mobile, and Switch versions, Restoration Potions are healing potions with a shorter cooldown.
- Likewise carry mana potions, if you use Magic.
- The Strange Brew is also an option, but its weak healing effect will trigger the Potion Sickness cooldown as well as Mana Sickness. On the Old-gen console version, Nintendo version, and tModLoader version, Restoration Potions can save a slot, but will likewise trigger both cooldowns.
- 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.
The Sky above the surface is highly recommended for the Twins arena, as vertical movement is required to dodge most of the attacks.
- A very long Sky Bridge (if possible made out of Asphalt or Frozen Slime Blocks) is optimal. Continuously running with Spectre / Lightning / Frostspark / Terraspark Boots causes both to miss you with their projectiles very often, and keeps each Twin at a stationary horizontal position most of the time, allowing you to fire continuously at it without switching your aim. Wings will help dodge each of the Twins' second phases. Using Asphalt can negate the need for Boots, while using them can allow you to avoid taking damage completely. However, try not to run too fast if you use Boots and Asphalt, as Retinazer may fall behind and despawn. Spazmatism, however, is fast enough to keep up. Regular stone blocks can be used too if you have obtained the Blessed Apple.
- The standard Boss arena of several layers of Platforms with furniture buffs makes maneuvering around easier.
- Also, a wall on both sides of a small area can block Spazmatism's cursed fire, but be careful not to run out of time from covering behind the wall. It is helpful to have a one block hole one block up to shoot through. This is more useful if you want to try tanking the boss with the above tip of heart statues. If you can tank the hits with the help of heart statues, you can gun down Retinazer while Spazmatism is only able to charge at you.
- A safety box in the ground isn't bad either, if you acquired the Daedalus Stormbow. That way you could attack Retinazer while its laser can't hurt you in the box. In order to attack Spazmatism make the box one block from the surface and bring Holy Arrows, the impact from the stars could hurt it. Stay close to the edge so the Cursed flames can't hurt you.
- The player can use a Minecart Track when building a sky arena to avoid The Twins' attacks whilst using a ranged weapon.
If a Mechanical Boss has been defeated, Life Fruits will begin to grow in the Underground Jungle, increasing life by 5 per Life Fruit until the player reaches 500 health. It is recommended to get as much Life Fruit as possible.
- Adamantite armor provides the greatest overall increase to all stats. Melee and ranged users should substitute in a Frost Breastplate to increase damage output and defense without sacrificing anything important.
- Titanium armor is a defensive alternative for Adamantite Armor, the Titanium Barrier / Shadow Dodgebuff increases survivability.
- Crystal Assassin armor has respectable defense and stat boosts, which makes this set a viable alternative to Hardmode ore sets. On Desktop version, it provides a dash as part of its set bonus, allowing players to replace Shield of Cthulhu with another accesory.
- Orichalcum armor provides very high critical strike chance and its set bonus can hit both eyes.
- Palladium armor provides lower stat bonuses, but the Rapid Healing buff greatly increases natural regeneration.
- Hallowed armor becomes a great choice if a Mechanical Boss has been defeated. The Holy Protection in the Desktop version allows the player to dodge an attack.
- Spider armor is the best choice for summoners who do not use whips frequently.
- Obsidian Armor provides strong bonuses and high minion damage to summoners. The increased whip range and speed can potentially outperform Spider Armor.
- The armor sets available from the Tavernkeep combine summoning with one of the other classes. This is only available if you've defeated another mechanical boss.
- Forbidden armorand Frost armor() provide weak stat bonuses, but allow you to mix different damage types. On Desktop version, the Frost armor provides excellent stat increases as a set bonus, making it a strong alternative to Adamantite or Titanium armors.
- For Melee users
- The Shadowflame Knife shoots very fast and deals a lot of damage per dagger. It also inflicts Shadowflame, which deals 15 damage per second, more than any other debuff available. If aimed right, it can manage to hit both eyes at the same time.
- Ice Sickle could also be used, as Spazmatism will spend most of the time behind the player, so shooting constantly backwards with the piercing projectile will hit him multiple times and deal quite reasonable damage.
- Alternatively, Light Discs can work too, if you already defeated The Destroyer.
- Yoyos with the Yoyo Bag can be useful.
- Dao of Pow and Drippler Crippler can be an excellent choice due to their high damage and range. However, they can be harder to acquire than other options available.
- If Duke Fishron has been defeated, the Flairon makes the fight trivial.
- For Ranged users
- The Adamantite or Titanium Repeater with Holy Arrows or Ichor Arrows are great for players who have yet to beat a Mechanical Boss.
- Hallowed Repeater is a good option if a Mechanical Boss has been defeated.
- Guns such as the Megashark, Uzi, Gatligator, and Clockwork Assault Rifle can be quite effective when paired with Ichor, Crystal, or Cursed Bullets.
- Keeping an Endless Musket Pouch and Endless Quiver allows the user to have backup ammo in case the player runs out of special ammo.
- Daedalus Stormbow is a great bow, especially if combined with Holy Arrows, even better with a Magic Quiver and its upgrades, as these three together can take down any of The Twins in seconds.
- The Sharanga with Wooden Arrows will be very useful as well, as it turns into Spectral Arrow.
- The Dart Rifle /Dart Pistol with Crystal Darts or Ichor Darts is an effective weapon, especially the former, which can hit both Twins at the same time.
- The Onyx Blaster with Exploding Bullet is a great combination, and will deal over 250 damage per hit.
- If Duke Fishron has already been defeated, the Tsunami makes the fight trivial.
- For Magic users
- Sky Fracture is one of the strongest weapons mages can use in early Hardmode.
- The Meteor Staff and the Crystal Serpent are also very powerful choices.
- The Spirit Flame 's homing abilities and high damage allows the user to deal consistent damage.
- The Shadowflame Hex Doll can also be very strong, despite its short range.
- Golden Shower inflicts the Ichor debuff, decreasing the defense of The Twins.
- The Nimbus Rod's rainclouds last for 1 minute, adding DPS.
- If a Mechanical Boss has already been defeated, the Unholy Trident is a powerful choice if aimed correctly.
- If Duke Fishron has been defeated, the Razorblade Typhoon makes the fight trivial.
- The Bubble Gun, another Duke Fishron drop, can easily defeat Spazmatism, but struggles against Retinazer.
- For Summoners
- The Spider Staff is the best summoning choice because the spiders will latch on while they change forms, dealing hundreds of damage. Note that your arena will need to include background walls to make full use of the spiders.
- The Sanguine Staff is the best summoning choice for those who don't want to make a background wall arena, its perfect tracking and high base damage makes it a powerful choice.
- The Blade Staff, while weaker than the Sanguine Staff by itself, can greatly outperform it with whips that deal summon tag damage.
- Snapthorn's Jungle Fury buff increases the speed of whips, adding more DPS.
- The Firecracker increases damage output for minions, especially with ones that have high base damage such as Sanguine Staff.
- Durendal is a powerful choice if a mechanical boss has already been defeated, and if combined with other whips, makes it a potent weapon.
- The Queen Spider Staff sentry adds extra DPS, while not counting towards minion count.
- If a Mechanical Boss has already been defeated, the Ballista Cane is a powerful choice when facing the Twins.
Accessories that improve mobility are a must, since the Twins use quick attacks.
- The Amphibian Boots, Frostspark Boots, or Terraspark Boots and Wings are a must, especially for the Sky Bridge method. They allow the player to dodge, and also allow the player to flee temporarily if health is running low.
- The Gelatinous Pillion can replace both the boots and the wings, as its quick vertical movement makes it excellent for dodging the flames from Spazmatism in the first stage and flying out of range in the second stage.
- Even though it doesn't prevent Cursed Inferno, the Ankh Shield can still be used to prevent Knockback and for some useful extra defense.
- An Emblem of the player's respective class greatly increases damage output.
- Shield of Cthulhu's dash is essential throughout the fight.
- Worm Scarf greatly decreases damage, but is exclusive to Corruption worlds.
- The Brain of Confusion is very useful for Expert Mode players with Crimson, as it provides a chance to dodge an attack . It doesn't prevent getting inflicted with the Cursed Inferno debuff, however.
- The Charm of Myths reduces the cooldown of Potion Sickness as well as increasing passive health regeneration.
- It can be quickswapped in the accessory slot if using it on a vanity slot, taking advantage of its reduced Potion Sickness cooldown.
- The Cross Necklace or the Star Veil increases invulnerability frames for a brief period upon taking damage, which can greatly mitigate alot of damage, especially from Spazmatism's charges.
- The Moon Charm gives a increase to various stats, increasing survivability and damage.
- The Magic Cuffs (or Celestial Cuffs) are helpful if using Magic Weapons, but requires the user to take damage.
- Magnet Flower, Arcane Flower, Mana Cloak, or Mana Flower allows the user to automatically consume mana potions.
- Magic Quiver and its upgrades greatly increases arrow damage.
- Pygmy Necklace adds an extra minion slot.
- Feral Claws / !!Error: Invalid EICONS input! Titan Glove and its upgrades enables autoswing and increases melee and whip knockback and size, making it useful for both Melee and Summoners.
If possible, reforge all Accessories for damage, crit chance or defense bonuses. If money is no object (see Guide:Making Money), having all Accessories reforged to Warding, Lucky or Menacing provides an extra 20 defense, 20% crit chance or 20% damage (24%, since the Demon Heart allows you to have 6 accessories, up to 28% in Master Mode with 7 accessory slots).
- Regeneration Potion, Endurance Potion and Ironskin Potion will help prevent fatal damage. Two of each will likely cover the entire night.
- Any food item providing the Well Fed buff is very useful.
- Gravitation Potion can be especially useful, as it eliminates the need for any arena and may free up an accessory slot.
- Swiftness Potion greatly increases mobility.
- If you have access to a world with Corruption, a Wrath Potion is a good bonus, but not necessary.
- For magic users, a Magic Power Potion and a Mana Regeneration Potion are a must.
- Archery Potion will greatly boost the damage and speed of Arrows.
- Melee users greatly benefit from the effects of an Ale or Sake
- Summoning Potion adds an extra minion slot to the fight.
- Because the Twins are vulnerable to many debuffs, melee and summoners can use Flasks. The Flask of Ichor for Crimson worlds greatly increases the damage output of all weapons, and the Flask of Cursed Flames for Corruption worlds can give a very slight increase to DPS.
- Crystal Bullets and Ichor Bullets are a must-have if using guns, and Holy Arrows and Ichor Arrows for bows.
- The Ice Rod is useful against Retinazer because the spawned ice blocks can block its lasers.
This strategy requires you take out Spazmatism first. Once you defeat Spazmatism you need to get Retinazer into its second form. Then go inside a small box of solid blocks and use Summons (preferably with summon armor), the Meteor Staff or the Daedalus Stormbow (preferably with Holy Arrows and the Magic Quiver / its upgrades) to take down Retinazer. Because Retinazer does not charge in its second form and its lasers do not pierce blocks, you will be completely safe.
Close-ranged Unicorn Strategy
A helpful strategy is a Skybridge using a Blessed Apple and any kind of yoyo (A Yoyo Bag is recommended) or a long range weapon. Running with the Unicorn and shooting the yoyo behind you will deal a lot of damage, and you won't get hit very much as the unicorn is slightly faster. Warning: Using this strategy may lead to the The Twins despawning if you go too fast.
A strategy that is helpful for all classes is to use a minecart track extending as far as possible. For shorter minecart tracks, both ends can be hammered to allow the minecart to go in both directions without losing speed. As the minecart can go faster than The Twins, the player can use a long range weapon, such as a Repeater or a Yoyo (with Yoyo Bag) to deal damage from a relatively safe distance. Warning: Using this strategy may cause The Twins to despawn if that player travels too fast.
After gaining access to the Tier 2 equipment sold by the Tavernkeep, The Twins becomes much easier to defeat. Wearing the Squire armor and using the Ballista Cane will give the best results because of the high defense and health regeneration provided by the armor, as well as the Ballista Panic! buff doubling the firing rate. Acquiring one of the accessories dropped by the Ogre is recommended for this method. When building your arena, be sure to use platforms whenever possible to maximize the opportunities your Ballistas have to fire. Make sure that you have Heart Lanterns and Campfires set up to give yourself the most health regeneration. Having a good pair of Wings, the Cobalt Shield or its upgrades, and the Lightning Boots, Frostspark Boots and Terraspark Boots are recommended for maximum mobility. The Summoner Emblem will make the fight go much faster, rounding out your accessories. A few Greater Healing Potion are all the healing you'll need in case you get backed into a tight spot. Once the Twins have been summoned in, simply kite them around your Ballistas, taking damage periodically, preferably from Retinazer's laser for minimal damage. With the best Modifiers on your gear and all the relevant buffs, the Twins will go down in two to three minutes. If you find yourself taking too much damage and needing to heal more, consider swapping out the Summoner Emblem with a Charm of Myths so you can heal more often.
Invincibility Machine 
Warning: Some players consider invincibility machines cheating.
After defeating a few Biome Mimics, you should have the Fetid Baghnakhs and the Daedalus Stormbow. With two Target Dummies and a block overhead, you can make the invincibility machine. Get a Slimy Saddle and try to bounce on both dummies while keeping it rapid. After you summon the boss, use the Fetid Baghnakhs to quickly take out Spazmatism. Then use the Daedalus Stormbow to beat Retinazer.
Note: In the 1.4 update, this glitch was changed to be much harder to pull off. Try this at your own risk, as it might not work.
The Black Spot
It is very easy to defeat The Twins with The Black Spot. The only thing you need to defeat them is high, consistent damage until dawn. Keep in mind that circling around in the skies may summon a Wyvern, so it's nice to have a weapon against segmented enemies (such as the Medusa Head).
Note: The Black Spot was nerfed to be slightly slower in 1.4.1, which may result in taking more damage than intended.
Bouncing Strategy 
It is very effective if you are able to keep The Twins low to the ground to bounce on them repeatedly using a Slimy Saddle. It works especially well to pair this with the Meteor Staff, raining meteors down on whichever eye you happen to be bouncing on.