Skeletron

Skeletron is a boss which can be 'summoned' by talking to the Old Man in front of a Dungeon at night. If you choose 'curse' when talking to him, he will immediately transform into Skeletron and start attacking you, so be prepared when this happens. This is a difficult boss, do not try to fight him unless you have lots of potions, end-game equipment and/or throwable objects.

It is also notable that Skeletron is currently the only boss that can only be summoned and defeated once per world.

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When you defeat Skeletron, you will gain access to Dungeons, and the Clothier NPC will come to your town.

Attacks
Skeletron will attempt to hit you with his arms by swinging them at you and will sometimes spin his head, put his arms in the air, and chase you with his head. If you take too long to kill him, and the sun comes up the next day, Skeletron will hit you for 9999, killing you instantly.

==Tactics ==

There are a few things to keep in mind while fighting this boss with any technique.

First, try to keep the fight on a nice flat surface. it makes Skeletron's attacks far easier to dodge and makes attacking him just as easy. Secondly, watch out for his hands, as they will usually hit you the most often. Lastly, always watch for when he rolls his head towards you. while attacking like this, he is extremely vulnerable, and you can even do quite a bit of damage with swords such as the Blade of Grass. Also, start your fight at the earliest possible at night because you need to defeat him before daybreak.

One technique (and probably the most common) is to use ranged weapons. Simply spamming the ranged weapon at Skeletron's head while dodging his attacks is usually quite effective, especially if it's rapid fire. Good weapons to use would be the Pheonix Blaster, Star Cannon (assuming you can afford the strange form of ammunition), and the Space Gun. the Molten Fury is also a good choice. Shirukens and Throwing knives a possible but challenging way to kill Skeletron earlier in the game.

Another technique to better conserve ammo is to use ranged weapons to attack Skeletron's hands first, and then deal with the head using using swords that can hit behind you, flail weapons or weapons that return to you, like the Flamarang.

Tips
It is recommended that you do not wear Necro Armor for this fight, as it changes the sound you make when you are damaged to same one that Skeletron makes. This can result in you not noticing when you take damage, especially if you're using the Cobalt Sheild. One solution to this problem is to wear something else in the Vanity Slot, as this prevents your damage sound from changing. During the fight, if you don't have a Minishark, or another powerful weapon, it is useful to take down his arms/hands. After this, it will just be his head that you will deal with, thus making the fight easier since you will just simply jump and not be damaged.

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If you try to go into the dungeon by going through the main entrance or by digging in without defeating Skeletron first, one or more Dungeon Guardians (which looks like spinning Skeletron heads) will ram into and kill you along with any other players who may be nearby. the Dungeon Guardian is physically impossible to dodge, and your death can only be delayed by a few seconds, if you're lucky.

The Dungeon Guardian only appers when you move in front of the dungeon's back wall below rock level, even if you placed it. using a Depth Meter can help in finding the exact level.Destroying the back wall with a hammer will prevent the Dungeon Guardian from spawning although being hit by other dungeon mobs will usually knock you over walls you have not destroyed unless you have a Cobalt Sheild equipped. One way to help destroy background tiles is to use Dynamite.

Bugs

 * An interesting graphical bug appears when you fail to kill Skeletron but survive (if he flies too far offscreen) and see the Old Man spawn, when you kill Skeletron, He will drop multiple headgibs, each dropping it's own items. Twotrons.jpg
 * If Skeletron spawns too far outside the dungeon, he will spawn with only a head.
 * As of 1.0.6 if you summon him too early (just when it turned night) he will automatically kill you like a skeleton head.

Trivia

 * In the Alpha version, the monster had 4000 health instead of 6000 and 3000 in an earlier Alpha. In the 1.0.5 patch, his head had 5,000HP, however this was changed to 4,400HP in the 1.0.6 patch.
 * This boss is currently considered the hardest boss to beat, due to his massive health. He is also the most rewarding since defeating him grants access to the dungeon which can hold some of the best items in the game.