Butcher

It only appears during a Solar Eclipse, and only once Plantera is down, so the eclipses you survive earlier in Hardmode will never produce any. There is no summoning item for it. It arrives with the event, walks in from the edge of the screen, and comes at you on foot.

It builds speed the longer it runs, which is normal enough. What catches people is that damage speeds it up too, on a smooth curve, so by the time it is nearly dead it moves about twice as fast as it did at the start. The last few hits are the dangerous part of the encounter rather than the safest. You cannot juggle it either: any vertical movement at all makes it completely immune to knockback.

The chainsaw has its own hitbox and hits noticeably harder than the body, so being caught on the blade side is worse than a glancing bump. It opens doors and tall gates in a single swing and reaches through a single tile of wall, so a thin panic box is not shelter. Build two tiles thick or fight it at range.

• The reference is Leatherface, though the mask and apron are much closer to the killer from Motel Hell.
• The chainsaw it drops throws sparks on contact. The one it is carrying does not.