Guide:Skeletron Prime strategies

Skeletron Prime, the Hardmode version of Skeletron, is a difficult boss with high damage, HP, and defense. Depending on your personal abilities, this may be the most difficult boss in the game.

Boss
Skeletron Prime is a flying boss that consists of five parts:
 * Prime Vice, a melee arm, with 10000 health.
 * Prime Saw, a melee arm, with 10000 health.
 * Prime Laser, a ranged arm that fires lasers, with 6000 health.
 * Prime Cannon, a ranged arm that fires bombs, with 7000 health.
 * Skeletron Prime, the head, with 30000 health.

Note that to defeat Skeletron Prime, only the head needs to be destroyed. Doing so may be difficult if you are trying to keep your distance, as shots will frequently hit the interposing limbs. With powerful weapons it is entirely possible to destroy all four limbs and the head in one night with plenty of time left over.

Equipment
An optimal gear build for fighting Skeletron Prime for the first time without gear from other Hardmode bosses would be:

Armor: Full Adamantite armor, with the ranged or magic helm. The use of melee is not recommended due to the high contact damage, two melee arms, spinning head attack, and the requirement for close proximity.

Weapons: For ranged, Adamantite Repeater with Cursed Arrow, as they have the highest base arrow damage, and the Cursed Inferno debuff can be applied to the boss's arms. A Megashark with Crystal Bullets, which allows for greater accuracy and damage over arrows. For magic, Laser Rifle or Crystal Storm are preferred due to the rapid fire rates and long ranges. Again, melee is not recommended.

Accessories: Optimal accessories can vary based on playstyle and availability, but some are highly recommended, such as:


 * Obsidian Shield for added defense as well as knockback immunity.
 * Angel Wings/Demon Wings for high speed flying maneuverability and slow fall.
 * Ranger Emblem/Sorcerer Emblem for the 15% damage increase.
 * Mana Flower for the reduced mana usage and auto mana potion consumption (if using magic).

Other useful accessories include:
 * Spectre Boots
 * Philosopher's Stone
 * Band of Regeneration
 * Star Cloak
 * Cross Necklace

These should be reforged for defense or damage, possibly movement speed if not using Spectre Boots.

Potions: As with all bosses, potion buffs are easily acquired stat boosts that help significantly. The following should always be used:
 * Greater Healing Potion
 * Ironskin Potion
 * Regeneration Potion
 * Bowl of Soup
 * Gravitation Potion
 * Swiftness Potion

The following are useful, but not required:
 * Hunter Potion
 * Night Owl Potion
 * Shine Potion

PLight's Method
Both of the flying hardmode bosses are likely best solo'd by air while running primarily in one direction. As such, a two or three level skybridge made of wooden platforms running a significant length of the map would give the player a distinct advantage. While gravitation potions would effectively allow you to combat the bosses by air, it can be difficult to work out the leading with ranged weapons while flipping gravity, and Prime's motions are somewhat more predictable if running on a mostly level surface instead of flying all around. This is important - even if ammunition is not a limiting factor, time certainly will be. Once day breaks, his damage goes to over 9000 and his defense renders most of your attacks useless. Hermes Boots are required for the skybridge method - that or a Anklet of the Wind, Aglet and Swiftness Potion or four. Any accessories you bring should be reforged to have greater combat power. A well-functioning build consists of full Adamantite armor (melee), a Hallowed Repeater + Cursed Arrows or Hellfire Arrows, a Megashark and/or Clockwork Assault Rifle + Crystal Bullets/Cursed Bullets/Meteor Shot (Crystals have splash damage, but less damage than cursed on average, and lack the Cursed Inferno debuff, while meteors can pierce multiple targets - which is useful for this boss as his orbiting limbs will often get in the way of your attacks), as well as an Adamantite Glaive/Excalibur if you feel like trying to melee. For potions, Ironskin Potions, Regeneration Potions, Thorns Potions, Swiftness Potions, and Gravitation Potions are all useful. Be sure to bring a stack of Greater Healing Potions as well. For accessories, I personally used Angel Wings, Spectre Boots, Obsidian Shield, Cloud in a Balloon, and Diving Gear, all of which had been reforged for defense or speed, and using this build I managed to get it down to 1300 health and kill the Prime Cannon and Prime Laser before sunrise, though I missed most of my shots. Using the outlined Skybridge method should make Prime easier to hit, however.

Necrodoom's Method
Since the main issue with this this boss is killing it before sunrise, ive decided to use a different type of arena, more focused on staying close to boss than running away from it.

The Arena
A box of wood platforms, allowing you to circle around the boss while not destroying your aim with a gravity potion. add a ceiling to block the prime cannon's shot and make it useless.

Items To Use
Most important is rocket boots or wings (rocket boots more recommended, boosts faster), this is the key in circling the boss, without it the boss will beat you up easily. take your strongest gun and remember that the boss has high defence.

The Battle
This is the order of priority of things to shoot at: 1. Prime laser 2. Prime saw 3. Prime head

Ignore the vice and the cannon, since cannon is made useless by ceiling, and the vice's AI will render itself useless against your constant circling.

Simply circle around boss, aim your gun at the prime laser, and pray for it to come down before you die due to using potions too fast. Once its down, the battle suddenly becomes much easier. Destroy the saw to prevent it from depleting the rest of your potions, and pound away at the head undamaged until its down.

TheBaron's Method
I recommend Skeletron Prime as your first Hardmode boss, as this will give you access to the Flamethrower, which will make quick work of The Destroyer.

Setup
The beauty of Terraria is that you control the environment. The setup for the arena in which to fight is simple, and identical to the one used to fight The Twins:
 * A base layer of solid bricks (I prefer Dungeon Brick) a respectable distance above the ground, with the purpose of keeping you in the arena and collecting possible monster spawns away from the actual battle. You should never actually run on this level since it will collect the bombs from the Prime Cannon, but you may have to drop down onto it temporarily.
 * A middle layer of wooden platforms 25 blocks above that. This is your drop level to escape a melee attack and/or let the boss pass over you. (Note: 25 blocks is the maximum safe distance for falling damage)
 * Three upper layers of wooden platforms, starting 25 blocks above your middle layer, with about 12-15 blocks inbetween. This is to provide multiple avenues to run backwards while firing at the boss.

The whole thing should be about 2-3 screens wide, and high enough to avoid monsters but not so high as to spawn Wyverns. You do not want walls on the sides, which will limit your maneuverability. The best place to be is the lowest upper layer of wooden platforms, which allow you to drop to avoid melee arms. The use of wooden platforms trivialize the Prime Cannon's bomb attack.

Assuming this is your first Hardmode boss, my gear recommendations are as follows: Note: All accessories should be reforged to at least 3% damage/3 defense/2% crit. Movement speed is made irrelevant by Spectre Boots, and melee speed/mana are useless to a ranged character.
 * Full Adamantite armor with Adamantite Mask
 * Deadly/Unreal Adamantite Repeater with Cursed Arrows
 * Ranger Emblem
 * Obsidian Shield
 * Band of Regeneration
 * Spectre Boots
 * Angel Wings/Demon Wings

All combat buffs, such as Ironskin, Regeneration, and Well Fed are mandatory, as well as use of Archery Potions. To avoid having to place solid blocks for torches, use Shine/Night Owl/Hunter potions.

Wait until you hear the music change to indicate nightfall, consume your buff potions, then use your Mechanical Skull.

Combat
The key is damage avoidance via high maneuverability. You have two methods of dodging attacks:
 * Moving laterally (as in, side-to-side}
 * Moving vertically (as in, up and down)

In order to avoid laser shots, never stop moving. Skeletron Prime likes to hover above you, reach out with his melee arms, then rush past you. Dropping down vertically is a good way to avoid this when he is trying to overtake you. Backtracking at full speed with Spectre Boots on the sky bridge will also allow you to fire at a consistent angle. Basic attack pattern should be: Sometimes you may have to break out of this pattern to avoid contact, or you may have to move laterally while flying above the arena.
 * Move laterally backwards while firing at head.
 * When boss approaches close, move vertically to avoid contact. Drop down to the middle layer. If you dropped last time, fly up.
 * Continue in a circular pattern until you destroy the head.

You should always target the head. While other arms will occasionally absorb hits, finishing combat quickly is important. Note that the melee arms can get a significant distance away from the head and ranged arms.

Also, a personal rule of thumb for using Greater Healing Potions is as soon as you see only one row of hearts, use it. This will bump you to around 350, and your regeneration will still have use topping you off.

Afterwards, use the Souls of Fright to make a Flamethrower for use on The Destroyer.

Krazl's Melee Method
Requirements: Light Discx5, Adamantite Armor, Band of Regeneration, Cross Necklace, Regen Potion(s), Ironskin Potion(s), Meteoritex100ish

Optional: Star Cloak, Spectre Boots, Angel Wings, Health Potion(s), Delicious Soup, other defensive accessories

Step 1: Prepare for battle!

Create a single line bridge of meteorite preferably 100ish or more blocks long. If preferred wall off the edges and place doors at the bottom. This arena will be used for all of the hardmode bosses.

Step 2: Fighting like a man...with a brain

Instead of flying around with antigravity potions and using ranged weapons like some elf, make sure you do not have an obsidian skull/shield/horseshoe equipped. As such you will constantly be taking 1 damage from standing on the meteorite floor and will be invincible for most of the fight. This will also proc the Star Cloak if you have it equipped. Make sure to start this fight as close to 7:30pm (night's in-game beginning) as possible for maximum time to fight the boss. I definitely recommend consuming a bowl of soup for this fight. Avoid jumping unless absolutely necessary to escape his spinning spiky head. In the mean time focus exclusively on his head and ignore the arms. If you stay on one side of your arena until he spins his head, you can then move him to the other side while damaging him and repeating the process from the other side.

Theothersteve's Flying Megashark Method
I strongly recommend beating this boss last.

Like the Twins, this boss is probably most easily fought in the sky using Gravity Potions and a Megashark. You can expect to go through about 600 Crystal Bullets for this fight with that weapon; bringing a full 1000 bullets (all four ammo slots) should be safe. Also bring Ironskin Potions, Regeneration Potions, and Greater Health Potions. A Bowl of Soup is also helpful. Equip full Adamantite armor with a mask for the ranged bonus. Recommended accessories are Wings, Ranger Emblem, Spectre Boots, Obsidian Shield, Cross Necklace, and/or Cloud in a Balloon.

Keep your distance, and shoot anything that you can. Drink potions as soon as potion sickness wears off. Use the quickbuff button to keep all potions active on you. When you approach the ground or outer space, switch directions. If you get too far away to shoot Skeletron, switch directions back and forth to allow him to catch up.

For your first fight, your best bet is to eliminate all of the limbs before going in for the kill. Note that once all four limbs are dead, you can quickly and safely pour ammunition into his skull until he's dead.

If you are still having trouble, make a small hut with a bed and move the Nurse NPC there. Bring a magic mirror and a gold coin. Whenever you are in danger of dying, use the mirror, heal at the Nurse, then run back out and continue fighting.

With full Hallowed armor and some experience, it's possible to use this method without the Nurse, with only normal Health Potions, and kill Skeletron Prime twice in one night.

Pure Melee Method
A method for those who may want to kill Skeletron Prime in pure melee combat, without the fire block exploit and even without ranged melee weapons. However, ranged weaponry such as Light Discs can make the fight even faster.

Requirements:
 * Gear
 * Legendary Excalibur
 * Melee Adamantite armor set
 * Accessories of your choice concentrated on melee DPS and defense
 * Consumables
 * Ironskin Potion
 * Regeneration Potion
 * Bowl of Soup
 * Greater Healing Potion
 * Arena preparation
 * 1-3 Heart Statue(s), wires and a timer
 * Simple arena; Roughly 25x25 blocks of empty space

Tactics:
 * Install all your timed heart statue(s) at one end of your arena.
 * Killing Prime Saw is the first priority, for it is the only threat in this fight. Prime Saw AI will be on you most of the time, while the other hands are mostly hanging around harmlessly. Your defense also mitigates most of the damage from the other hands.
 * At the start of the fight, stand on your statues. Skeletron Prime will hover ~25 blocks above you. Wait for him to start spinning towards you. Let him close into melee range and start moving towards the other end of your arena while damaging him with Excalibur. He will stop spinning after ~25 blocks and go back to hovering above you. Return to your statues. Repeat until Skeletron Prime dies. With practice, you can kill 3 Skeletron Primes in one night.

Notes & numbers:
 * Excalibur is the only high-damage sword which allows you to swing it and move away from your target without turning, making it ideal for this fight.
 * You should be critting Skeletron Prime for at least 110 while he is spinning.
 * You should have at least 75 defense with your buffs on.
 * Heart Statue spawns a 20 hp heart every 10 seconds. Thus, a heart statue is comparable to 2 HP/s of regen.
 * Greater Healing Potions are comparable to 2½ HP/s. (3⅓ HP/s with Philosopher's Stone.)
 * With good movement and/or multiple heart statues, you won't even need healing potions.