Mecha Mayhem
Uncommon13.4%ObjectiveOptionalAnywhere
Do battle against the Twins, the Destroyer, and Skeletron Prime simultaneously and emerge victorious.
All three mechs at once - summon the Destroyer, the Twins and Skeletron Prime together (three summon items, one night) and win. Do it well post-Plantera when your gear outclasses them: the Destroyer dies first to anything piercing, then the Twins, then Prime. A long asphalt runway plus wings, or the classic slow-falling gravitation-potion box, keeps the chaos survivable. Comfortably easier than it sounds once you're in beetle/spectre-tier kit.