Vile Spit

Corruptors launch these globs at you, so the only place you meet one is a Hardmode Corruption. A Crimson world has none at all unless you have hand built a patch of Corruption yourself. Expert worlds add a second source: the Eater of Worlds spits them out during its fight, and they are a large part of why the Expert version of that fight feels so much busier than the normal one.

The glob travels flat and straight, and it pops the instant it touches a block, so any scrap of terrain between you and the shooter absorbs it. It also has health. The game files it as an enemy rather than a projectile, which means a sword swing, a stray pickaxe hit or a passing minion will delete it outright. Shoot them down when several are in the air at once instead of trying to weave through. Getting clipped by a Corruptor glob can leave you Weak for a moment, a small loss on its own but a bad one while you are clearing a chasm.