Winds of War Achievement

This is easily done with the Protector. One of his special abilities (unlocked with Nimp Relics) is called Western Wind and summons a tornado. If there is a fire or poison on the ground when you summon it, the tornado will become elemental. You could also throw a Lightning in a Bottle at it while it is summoned. Some enemies use this ability against you as well, and you can get it by transforming their tornados as well.