Gasbag

Gasbags are large stationary enemies which are indigenous to the Corpse only. They attack by breathing and then exhaling out large clouds of lingering toxic gas, similar to the gas left by Sick Boom Flies. Toxic gas damages Isaac if he stays within it too long, which is indicated by Isaac slowly turning green and a poison symbol above his head. Upon death, they release more toxic gas, limiting movement space when dealing with other enemies.