Bloody Spine

The Bloody Spine is a consumable item used to summon the Brain of Cthulhu. It can be crafted at a Crimson Altar from the Vertebrae dropped by Blood Crawlers, Face Monsters, and Crimeras. Although the Brain of Cthulhu dissapears if you try to escape from the underground when spawned by breaking Demon Hearts, you can use the Bloody Spine also on the surface and the Brain of Cthulhu will still appear.