I had this crazy Idea the other day. When you Defeat The Eye of Cthulu, You get a Yellow Gem piece. When you Defeat The Eater Of Worlds, You get a Blue Gem piece. When you Defeat Skeletron, You get a Red Gem piece. When you Combine all 3 Gemstones at a demon altar, You get a Gem. When you combine the Gem with the Voodoo Doll, you Get a Doll of Power. THIS Is used to Summon WOF. And,for Hardmode, When you Defeat the Twins, You get a Sacred piece, Along when You defeat Skeletron Prime and the Destroyer. Combine all the Sacred Pieces and get a sacred gem. Use the Sacred Gem to Destroy the Corruption.