The Destroyer is the Hard mode version of the Eater of Words, and is summoned with the Mechanical Worm. The Mechanical Worm is made with 7 Souls of Night, 6 Rotten Chunks, 5 Copper Bars, and 5 Iron Bars. He can only be spawned at night, and MUST be defeated before dawn. He, unlike the Eater of Worlds, can be spawned anywhere, not just in the Corruption. He also has probes that sprout from him and attack you. This is the reason that you will want a flail for the battle, recommended is the Dao of Pow, which can be made pretty early with light shards, dark shards, and Souls of Night and Light. You will need Mythril Armor or better to survive his many body sections. If you don't want the Dao of Pow, any high damage spear will work well because flails and spears can hit through multiple body sections at a time. And as with any boss of challenge, stack up on Potions that will buff you up like Ironskin.