Swamp Thing

There is no summon for it and no biome to find it in. It only turns up while a Solar Eclipse is running, which means Hardmode, so it arrives with the rest of that daytime crowd and leaves at dusk with them. It is one of the more common things in the event, so you will see several per eclipse.

It closes faster than almost anything else on the ground. By the time it is on screen it is already on you, and the pauses it takes are not openings, just a beat before the next sprint. Walking away from it does not work, and neither does dropping into a hole.

• Knockback. Anything with push stops a charge outright, and a fast firing weapon keeps it pinned for as long as you hold the button down.
• Height. It has no way to reach you, so a platform a few blocks up removes its approach entirely. Fighting one in a corridor gives you a single exchange and no second chance.

The name and the look come from the DC Comics character who first appeared in 1971 and got his own film in 1982. It used to be one of the sources of a Broken Hero Sword, which it no longer drops, so do not build an eclipse farm around it for that reason.