Mechanical bosses

Mechanical Boss it a term which refers to any of the three Hardmode bosses that can be summonded by "Mechanical" items. Once Hardmode begins, they will begin to spawn randomly until each individual one is defeated at least once. After defeating a Mechanical boss, Plantera's Bulb will grow.
 * The Twins - Summoned with a Mechanical Eye. Spawn message: "This is going to be a terrible night..."
 * The Destroyer - Summoned with a Mechanical Worm. Spawn massage: "You feel vibrations from deep below..."
 * Skeletron Prime - Summoned with a Mechanical Skull. Spawn massage: "you feel the air getting colder around you..."