You touch a metal weapon worth at least 2sp or a suit of heavy or medium metal armor, and it begins to glow red hot, creating an area of superheated air within a 10ft radius sphere around it. Any creature that ends its turn in the sphere must make a Constitution saving throw, taking 3d6 fire damage on a failure, or half as much on a success.

When a creature without resistance or immunity to fire damage tries to enter the sphere on its turn, it must first make a Constitution saving throw. On a success, the creature enters the sphere and takes 1d6 fire damage, and cannot enter the sphere on a failure.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for each slot level above 3rd.