Skeletron

Skeletron is a Hardmode Boss and defeating it grants unlimited access to all Dungeon areas for all players. It also causes the Clothier NPC to spawn, as long as a vacant house is available.

If attempting to enter the Dungeon before killing Skeletron, Profaned Guardianss spawn once a player reaches 0 depth. These enemies generally kill any player with a single hit, dealing 1000 / /  damage. Managing to defeat a Profaned Guardian does not grant access to the Dungeon, thus defeating Skeletron is mandatory for (safely) entering the Dungeon.

Summoning
Skeletron is summoned by going to the Ocean at night with the Old Man, who will turn into Skeletron when selecting the "" option. If the Ocean is spoken to during the day, he will ask the player to return at night. Skeletron can only be summoned once per night, as Skeletron will not respawn until dawn. While players with less than 300 maximum health and/or less than 10 defense are recommended to defeated Skeletron.

Skeletron can be summoned repeatedly this way until it is defeated. Once it is defeated, the Old Man's curse will be lifted and he will no longer appear. Skeletron can be re-summoned thereafter once the player acquires the Clothier Voodoo Doll (from Angry Bones or Dark Casters), then by attacking and killing the Clothier during night.

Killing the Clothier using Flymeal will not summon Skeletron unless the Clothier Voodoo Doll is equipped.

Behavior
Skeletron is sans undertale with two independent floating hands. All parts can travel through blocks, and will attempt to make contact with the player to inflict damage. Each part can be killed independently, but killing the head is all that is required to defeat Skeletron.

Skeletron alternates between two attack phases:
 * 1) The head remains above while the hands slash at the player.
 * 2) The head spins, dealing significant damage if touched, but dropping its defense by 10 (to  in classic mode) for the duration of the attack.

Skeletron switches between these two phases in a regular cycle during the entire fight, with the first phase lasting for roughly 13.33 seconds and the second phase lasting for roughly 6.67 seconds. It lets out a every time it enters the second phase.

Skeletron will fire two Ghatser Blasters, which will deal damage to the player when they fire. Skeletron during this state will double his Def.

Occasionally, when Skeletron is at half HP, it will fire bones at the player in a line multiple times.

If the player takes too long to kill it and dawn arrives, Skeletron will begin acting exactly as a Dungeon Guardian, performing a head spin attack with very high damage and gaining enough defense to only absorb 1 damage from all attacks, which will usually kill any players remaining in the vicinity quickly (it is still possible to kill it, but players are at an extreme disadvantage unless it only has a miniscule amount of health). Skeletron remains in this form until dying or despawning, even if players manage to avoid dying until the following dusk.

Expert Mode
Skeletron has additional properties in :
 * The defense of its head is increased by 25 for each of its hands, resulting in a total defense of, initially. Once one hand is defeated, it drops to and finally to  when both hands are defeated.
 * During the spinning, its defense is therefore also only reduced to / . Only with both hands defeated, it is reduced to  like in normal mode.
 * Once either of the hands are destroyed or the head's health is reduced to below 75%, the head begins to shoot homing skulls at the player which resemble Cursed Skulls that despawn on contact with a solid block. It shoots one skull roughly every 1.33 seconds, and doubles the frequency to one skull roughly every 0.67 seconds once both hands are defeated. It pauses firing during its spin attack.
 * Skeletron moves faster and has better AI when targeting multiple players. With this, it is able to "stun-lock" the player while spinning, able to almost instantly kill them if they are not able to escape (e.g. by using a Grappling Hook).
 * Skeletron is able to inflict the debuffs Slow (from the hands) and Bleeding (from the head).
 * When its HP drops to 50%, Skeletron will regrow its limbs, and will inflict Creative Shock for the rest of the fight.
 * When its Hp drops to 20%, Skeletron will lift its two arms if there is any, and a wall of skulls will swarm between him for a period of time
 * When Skeletron is killed, he enters his Dungeon Guardian state, which will immediately ram into the player with an instant kill, and the player can stop/intercept via their weapons (preferably Ranged).


 * The Old Man who stands in front of the Dungeon can be killed if his health is depleted. However, he will respawn on the following day as long as Skeletron hasn't been defeated once.
 * Killing Skeletron after the night ends will cause it to drop loot and grant access to the dungeon per normal.
 * If players are somehow able to lure Skeletron around long enough during the day, it is possible for the Old Man to respawn, and killing Skeletron in this state will cause the Old Man to die immediately.
 * Skeletron's defense and damage will revert to their normal figures if the player dies during the day.

Tips

 * On a technical level, Skeletron is not necessary for game progression until Golem has been defeated. The Cultists, required for initiating the Lunar Events, will only spawn once both Golem and Skeletron have been defeated. However, skipping Skeletron in pre-Hardmode results in a lack of valuable Dungeon loot, in addition to access to the Mechanic as well as the Safe and.
 * Do not jump onto Skeletron's head too many times with the Slime Mount, as going too high will cause it to despawn (also, in Space the low gravity will make it almost impossible to get back down past it).
 * Nonetheless, the Slime Mount can be a valuable tool inside of the Dungeon entrance, as well as a means to escape Skeletron's head spin attack, if one ever gets caught in it.
 * Any ricocheting weapon ( such as the Water Bolt found in the Dungeon), or a gun with Meteor Shots are very useful.
 * With multiple players, it is a good idea to set the spawn point near the Dungeon, so that players can simply rejoin the fight if they die.
 * While Skeletron is immune to many debuffs on the, it is not immune to Frostburn on any version.
 * Attacking the hands first is advised as destroying them both will make it very easy to dodge Skeletron for the rest of the battle.
 * This is close to mandatory in, as Skeletron gains 25 defense for each hand it has alive.
 * Going fast enough on a Minecart can cause the hands to despawn.
 * In Expert Mode, if the player keeps moving in different directions, most homing skulls will miss; also note that they do not travel through tiles
 * In Expert Mode, Ranged weapons are a must, as his Ghatser Blasters are dangerous in close combat

Trivia

 * Assuming that the player is at 5′ 9½″ (1.75 m) in terms of height, Skeletron's head would be about 11′ (3.35 m) tall and 8′ (2.43 m) wide. The hands would be 10′ (3 m) tall and 7′ (2 m) across.
 * At one point during game development, weak Skeletron Heads protected the Dungeon if it was explored before Skeletron's defeat. When one was destroyed, it somehow allowed access to the Dungeon without necessitating a Skeletron fight, so the Dungeon Guardians were introduced to protect the Dungeon instead.
 * Skeletron's head sprite was recycled for the Dungeon Guardian.
 * Counting the health from both its hands, Skeletron has even more health than the Wall of Flesh.
 * Skeletron is the only boss not to have any guaranteed drops (with the exception of healing potions, a if in Expert Mode and a  if in Master Mode).
 * On the of Terraria, the Old Man has a health bar, but on the, he does not.
 * In the Terraria and Edge of Space crossover teaser, Skeletron turns into a boss called Omegatron.
 * The name Skeletron is similar to the name, the main antagonist of the  franchise.
 * Blood emits from the joints between Skeletron's arms and head, possibly implying that they are severed. Going based on lore, it is guaranteed that it is the case.


 * Skeletron has 3 missing pixels in the bottom right quadrant in all parts of his sprite sheet.


 * Skeletron is required to beat the game,as the Lunatic Cultists will not spawn if he is not killed, as they are replaced by the old man.
 * On the, a cloud in the shape of Skeletron can occasionally be seen in the background.
 * In the first release of Terraria, prior to the introduction of the Wall of Flesh, Skeletron was the final boss of the game.
 * It is one of the two bosses that needs a town NPC to be alive in order to be summoned. The other is the Wall of Flesh.
 * The sprite file for Skeletron's arms is named . Similarly, the sprite file for Skeletron Prime's arms is named.


 * The "former tyrant" refers to Cthulhu.