Potion of Magma Form

Potion, rare

This burbling orange fluid transmutes your flesh into burning hot magma for 1 minute. Your own gear is unharmed by your magma form. While in magma form, you do not need to breathe and gain immunity to fire and poison and resistance to bludgeoning, piercing, and slashing damage from nonmagical attacks, though you also have vulnerability to cold and take 1d10 cold damage each round you end your turn immersed in water. You can move through spaces as narrow as 1 inch wide without squeezing.

Creatures or objects that strike you in melee while within 5 feet of you take 1d10 fire damage, and if you hit a creature in melee with your fist or a natural weapon like a claw or bite, you add 1d10 fire damage. A creature grappling you takes damage as above when it hits you with the attack it uses to grapple, plus an additional 1d10 fire damage if it is still grappling you at the end of its turn.