Alchemic golem, which is basically made out of potions. Its melee attacks expose you to random potion or potion vapor effects. Killing it drops a few random potions and causes more random vapor effects. It can spontaneously explode when it hits something, with a greater chance when you hit it in melee. The explosion obviously also causes multiple random vapor effects to the area, and scatters potions around (by throwing them, so they tend to smash if they hit anything).