Clinger

These are a hardmode fixture of the underground corruption and nowhere else. Nothing summons them and no event brings them out. They spawn on their own while you tunnel, already anchored to a block with the head riding out on a stalk. They never appear in surface corruption, so a surface farm will not produce a single one however long you leave it running.

Only the head is dangerous. The stalk it rides on is scenery, so you can stand right against the base of one without taking a scratch as long as the head is somewhere else. What it threatens you with is a slow orb of cursed fire that drifts through terrain and sets you burning with a debuff plain water will not put out. Those orbs cannot be shot down, so dodging is the only answer.

• The reach is not fixed. It holds a shorter length for a few seconds, then stretches noticeably further for a shorter burst before dropping back. A gap that looked safe will catch you on the next cycle, so give them far more room than they appear to need.
• Hitting one resets its firing timer. Anything with a quick rate of fire pins it down completely and it never gets a shot away.
• Breaking line of sight is the wrong instinct. If its timer expires while it cannot see you, it re arms almost instantly, so stepping back into the open gets you hit immediately. Keep the pressure on or leave the area.
• Lava does not touch them, like anything else that reaches through blocks, which rules out flooding a corridor and walking away.

Cursed Flame comes off a very short list of enemies, and this is the one you will actually bump into while digging out the corruption. The World Feeder is rarer underground and the Vile Ghoul keeps to the surface. If Cursed Bullets, Cursed Arrows or Cursed Darts are anywhere in your plans, do not walk past one.

It is the only enemy in the game that both drops cursed flames and uses them as a weapon. The behavior and the silhouette line up closely enough with Man Eaters and Angry Trappers that it reads as the corrupt counterpart to those.