Mechanical Skull

The Mechanical Skull is used to summon Skeletron Prime, a harder version of Skeletron. It can only be used during night time. Skeletron Prime must be defeated before the break of dawn or it will hit you for 9999 damage. Using another Mechanical Skull while Skeletron Prime is already spawned will result in instant death. It can also be used in a world without hardmode activated.