Psycho

He turns up during a Solar Eclipse once Plantera is down, and he turns up already hidden. Until you either damage him or walk within roughly ten tiles, he is a faint outline nobody picks out of an eclipse crowd. The first warning most players get is the knife landing on them.

That knife is the actual threat. The blade hits considerably harder than the rest of his body, so clipping past him is much worse than standing near him, and he sprints once the disguise drops. Keep him at range and kill him before he closes. He follows ordinary ground enemy behavior with one useful gap: he cannot use doors at all, not even during a Blood Moon, so a sealed arena shuts him out while much of the eclipse roster walks in.

• He is built on Michael Myers from the 1978 film Halloween, though the mask and the blade read closer to Jason Voorhees.