Guide:The Twins strategies

The Twins are the hardmode version of the Eye of Cthulhu. They are the mid-boss of the hardmode bosses, stronger than The Destroyer but weaker than Skeletron Prime.

Terrain preparation
The sky is a must when battling the Twins, as they must be dodged often.


 * A very long Sky Bridge (if possible made out of Asphalt or Frozen Slime Blocks) is optimal. Continuously running with Spectre/Lightning Boots causes both of the Twins 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 backward continuously at it. Wings will help dodge each of the Twins' second phases. When one Twin enters its second phase, defeat it before activating the other Twin's second phase. Using Asphalt can negate the need for Lightning Boots. Using Asphalt with Lightning or Frostspark Boots can allow you to avoid taking damage completely.
 * The standard Boss arena of several layers of wood platforms may be of use, though a skybridge would be preferred, as it allows firing and maneuvering in any direction. A solid ceiling just above your top platform will block Retinazer's beam attacks, as Retinazer always flanks from above.
 * If your arena is relatively small, hook up any heart statues and star statues you might have, with a 1 or 5 second timer. A minimum of three should be enough to keep you alive until the end of the fight. Bring mana/health potions to be safe.
 * 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.
 * If you have access to gravitation potions, this can easily eliminate the need for an arena, although the player's view flips instead of the player character (as of 1.2), this may make the battle very confusing.

Armor

 * Adamantite armor or Titanium armor should be used (or Hallowed Armor from another mechanical boss, But would highly suggest drinking an Iron skin potion if you are doing the fight alone). The defensive set bonus should generally be used, though those confident in their dodging ability may opt for the ranged bonus for extra damage. The frost set can be used it provides good defense and inflicts the frostburn debuff

Weapons
By this time you should have a reasonable amount of money, so you may want to invest some of it into modifiers for your weapons.


 * The Adamantite Repeater with Cursed Arrows or Frostburn Arrows is the optimal weapon for players who have yet to beat any Hardmode boss.
 * If you have beaten The Destroyer or have gotten lucky with Angry Trappers and in a Crimson world, the Megashark or Uzi with Ichor Bullets or Cursed Bullets are very highly effective ways to beat the twins if you're good at aiming.
 * The Sharanga with Wooden Arrows will be very useful as well, as it turns into Spectral Arrow, severely hurting the eyes.
 * The Megashark with Crystal Bullets is optimal if The Destroyer has already been defeated. Many of the Crystal Bullets' secondary shards will hit The Twins, causing much quicker damage than any other projectile.
 * Other weapons that work quite well are the Clockwork Assault Rifle with Crystal Bullets, because it has reasonable damage and a good range, and the Star Cannon, if you have enough ammo saved up. Even the Phoenix Blaster with Meteor Shot can be a viable weapon, provided that armors with ranged bonuses are being used, and the player is reasonably accurate.
 * The Clockwork Assault Rifle or the Gatligator can be reasonably useful with Exploding Bullets. Just keep your distance. Crystal bullets work well as well.
 * For magic users, the Laser Rifle is an effective magic weapon due to its fast firing speed, if you are lucky enough for it to drop from the Wall of Flesh. Cursed Flames is also a good idea because both Twins are vulnerable to Cursed Inferno. The Frost Staff is even better. Alternatively the Crystal Storm is an effective magic weapon that can be crafted before challenging any of the Hardmode bosses. Another good weapon for your first time facing the twins is the Unholy Trident. If you have crimson, a good idea is the get the Golden Shower, because The Twins are vulnerable to the Ichor.
 * For melee users, the Ice Sickle and the Death Sickle could also be used, as Spazmatism will spend most of the time behind you, so shooting constantly backwards with the piercing projectile will hit him multiple times and deal quite reasonable damage. Retinazer can then be taken down with the Light Discs or the Ice Sickle while he is behind the player, charging.
 * The Cutlass works well. But the Cutlass size would put you in a tight area, so use the Excalibur or the True Excalibur if you have Experienced a Solar Eclipse and have found a Broken Hero Sword

Accessories
Accessories that improve mobility are a must, since the Twins use quick attacks.


 * The Spectre 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 Obsidian Shield, the Cobalt Shield and Ankh Shield will prevent knockback.
 * The Charm of Myths is more helpful than you might think, as it provides a good health regeneration and reduced cooldown of healing potions, greatly increasing your healing potential.
 * The Cross Necklace or Star Veil is another good choice, as the Twins' frequent ramming moves deal a lot of rapid damage, and the extra period of invulnerability mitigates a significant portion of this damage.
 * The Moon Charm is very helpful if melee is to be used, as it will give a minor boost to all stats, raising your defense and therefore survivability, and also giving higher damage, so the fight can be completed faster.
 * The Magic Cuffs is helpful if you are using mana consuming items as you will take damage fuequenly from THe Twins

If possible, reforge all Accessories for damage or defense bonuses. If money is no object (see Guide:Making Money), having all Accessories reforged to Warding or Menacing provides an extra 20 defense or 20% damage.

Potions

 * At least seven Greater Healing Potions. Ten to be safe; this will be more than enough for any Twins fight.
 * Regeneration Potion and Ironskin Potion will help prevent fatal damage. Two of each will likely cover the entire night.
 * One Pumpkin Pie will likely last the entire fight, and it's easy to craft.
 * Gravitation Potion can be especially useful, as it eliminates the need for any arena and may free up an accessory slot (keep in mind you will need to prevent fall damage yourself when the potion wears off, if you unequip the Wings). Three of these will last the entire fight.
 * Swiftness Potion helps you evade the twins. Two should last the entire fight.
 * If you have access to a Crystal Ball, activate it just before the fight. It will likely last the entire fight.
 * If you have access to a world with Corruption on PC, a Wrath Potion is a good bonus, but not necessary.
 * For magic users, a Magic Power Potion is also a good substitute for Wrath Potions.
 * Because the Twins are vulnerable to many debuffs, melee players can take great advantage of Flasks. The Flask of Ichor greatly increases the damage output of melee weapons, and the Flask of Poison, Fire, and Cursed Flames will tack on even more damage.

The Battle
The Twins, as the name suggest, are two separate monsters, both of which must be defeated. They have a combined health of 43,000, shared between them. Retinazer, distinguished by its red iris, fires lasers. Spazmatism, distinguished by its green iris, fires cursed flames. When reduced to less than half health, they will transform, gaining a slight boost in offense and defense. They will not both transform at the same time; both must be reduced to half health for each to transform. When one is destroyed, the other will continue attacking in the same pattern. It is a great idea to take them out one at a time, because if they both end up in their second forms at the same time it can be very difficult to defeat them.

Retinazer
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 vertically with the player, positioned above them, which makes its shots easy to block with a solid ceiling.

When it changes into its second form, Retinazer will no longer engage in charge attacks. Instead, its lasers will fire with increasing frequency 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 (Preferably without fall damage), and you can be left unscratched. 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 more rapid and fast lasers that are therefore harder to dodge.

Spazmatism
Spazmatism, like Retinazer, varies between firing cursed flames from a distance and engaging in charging attacks. The flames do more damage than the lasers, but aren't as fast and thus easier to dodge. Spazmatism is always aligned horizontally with the player. The Spazmatizm would continuously shoot cursed flames at the player every second for about 8 seconds before slowly firing to 10-15 seconds per shot.

Spazmatism's second form changes his attack pattern dramatically compared to Retinazer. Its cursed flame attack becomes a constant stream of flame, which will last for several seconds. However, it doesn't chase the player quite 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. Dodging these charges is quite difficult. Much like Retinazer, fall as fast as you can while he is charging, and you should be okay. Misdirecting 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. Another tactic if in multiplayer is to have one player fly around him, distracting him while another fires arrows or bullets at him. (More effective once Retinazer is defeated)

Which to Defeat First
Defeating Retinazer first:

Pros: Retinazer has a ranged attack, and defeating this Twin first will assist players who are bad at dodging, afraid of lasers, or have a relatively low movement speed.

Cons: Retinazer has many, many lasers to dodge, and, in addition, if you are a slow player, can be the more deadly of the two Twins to fight.

Defeating Spazmatism first: 

Pros: Damage from Cursed Inferno can easily add up, so if you defeat him first, you won't have to deal with that for as long.

Cons: If you are a melee player (unless you have a melee weapon that shoots a beam such as the True Night's Edge), or slow, dodging the flamethrower vomit is potentially deadly.

Tips

 * Both Eyes, while not charging attack the player, stay in specific position relative to the player. And weapons such as Nimbus Rod are very useful, if combined with good tanking armor. The positions are:
 * Retinazer's first form will stay in either diagonally to the East or West from the player while not charging attack.
 * Retinazer's second form will stay directly above the player while normal attack.
 * Retinazer's second form rapid attack will stay at the east/west to the player, slightly moving vertically.
 * Spazmatism, in both forms will stay horizontally to the east or west of the player at normal attack.