Unknown Elixir

This bizarre blend of flavors reminds you of freshly cut grass, petroleum jelly, and honey. When consumed, it sits in your stomach like a rock and slowly swells in power. You gain the ability to cast one random spell of 6th level or lower, without expending a spell slot. This spell uses a save DC of 17 and a spell attack bonus of +9. The effects of this potion last until the spell is cast. This doesn't count against the number of potions you can have affecting your body at once.