Tentacle Spike

A hit leaves a spike embedded in the target that keeps ticking for several seconds afterward, and those stack up to five deep on one enemy. A target you keep swinging at gets steadily worse off even between your hits. Only the first enemy contacted per swing takes a spike, though, so sweeping it through a crowd does not spread them around.

It falls off common Corruption and Crimson trash at a rate low enough that you will never see one by accident. As a pre-Hardmode broadsword it is good without being so far ahead of what you can craft that a dedicated farm makes sense. Take it if it drops while you are clearing an evil biome anyway.

That seed raises the drop rate by a wide margin, and it is the one situation where deliberately farming for this is reasonable.

The name and tooltip come from Don't Starve, where the same weapon is torn off a swamp tentacle. The damage over time it applies is technically a nameless debuff, and it borrows another debuff's icon because it can never appear on a player.