[Name] Rotten World Gas [Source] Lollipop Chainsaw [Symptoms] 
A poisonous gas from the Rotten World (Hell) which leaks through interdimensional cracks caused by the Necromancer Swan when he cracks open a gate between Earth and Rotten World. This gas leaks through the cracks and kills everybody who inhales it within minutes, shortly reanimating them as psychotic zombies within a short while. It appears the gas is transmittable through bites, and therefore contagious. In hallucinations, the gas is also shown to affect animals.