Skeletron Head

Skeletron Heads are monsters that appear if you enter a dungeon before killing the Skeletron. If a player enters during the day, a Skeletron head will follow the player in the dungeon and deal up to 9999 damage to them, instantly killing them. During the night, large amounts of Skeletron heads will attack the player, dealing the same damage as the Skeletron boss's head. They will only attack once you are below the dirt layer of the World, so it is possible to take some Books and Chain Lanterns without any problem. Killing a single head will count as defeating the boss. This allows for players to earn their right to enter the dungeon if the old man isn’t present or never reappeared after failing to kill the boss.