Rancid water:Crafted by smelting Rancid Mixture----->Another item that should exist, crafted with Red mushrooms, rotten flesh, spider eyes, and sugar, to speed bacterial growth, would look like water, but opaque and a sickly green-brown, emitting green smoke and bubbles, and would be liquid death. Any mob that gets its head submerged, that means Steve too, would begin to start taking damage, randomly moving, and getting the "Nausea" potion effect, and would basically be marked for death. This could be used to create more compact mobgrinders, player-killers, whatever. ~Neuroticpig
That's a pretty good idea but I wouldn't want it to be obtainable, maybe just naturally occurring in swamp biomes or something because if anyone could get a hold of it there would be a lot more griefing.