Prime Directive

Summon with a Mechanical Skull (or wait for the natural night spawn). Prime is Skeletron with power tools: four limbs plus a spinning head. Either strip the vice and saw arms first for breathing room, or ignore the limbs and dump everything into the head before dawn - dawn kills you, not him. A big arena with campfires, heart lanterns and an ironskin potion carries it. Souls of Fright complete the mech set for Buckets of Bolts.