Skeletron

Skeletron is the boss that guards a world's Dungeon. If one enters the Dungeon before killing him, Dungeon Guardians will attack, causing 9999 damage, effectively killing the player with one hit. To summon this boss, you must talk to the Old Man at the entrance at night. The man will transform into Skeletron. If you attempt during the day, he will simply say "Come back at night if you wish to enter." or "I cannot let you enter until you free me of my curse".

Skeletron is a massive floating skeleton head with floating arms. He will try to make contact with the player with his head and arms. His head has 5,000 health points and 10 defense, and is the most resilient entity in the game with the exception of the Dungeon Guardians. Destroying the head kills Skeletron. He must be defeated before the break of dawn; all players will instantly die if he is still alive at that point.

Once you defeat Skeletron, you may enter the dungeon as many times as you like. You may not battle him twice on the same map, and must create a new one if you wish to fight him again.

When you kill Skeletron, the Clothier will move into a vacant House.