Theodorix's Magma

Your body heats up as you unleash a stream of molten magma, landing at a point you choose within range. Each creature in a 10-foot square centered on that point must make a Dexterity saving throw or take 3d6 fire damage, and the magma remains on the ground in a 10-foot square for 1 minute, dealing 2d6 fire damage to any creature that moves through it.

After the attack, you immediately revert back to your normal form. If you transformed while in mid-air, you will fall and take fall damage if you land more than 20 feet from the ground.