Whaleoil

You transform the flesh of a creature you can see within range into burning fuel. The target must make a Constitution saving throw. On a failed save, the target takes 6d10 necrotic damage and ignites in flames. On a successful save, the target takes half as much damage and isn’t set ablaze. While ablaze, the target sheds bright light in a 30-foot radius and dim light for an additional 30 feet. At the start of each of the target's turns, it and each creature within 10 feet of it takes 2d10 fire damage. At the end of each of its turns, the target can make a Constitution saving throw. On a success, the spell ends. If you target a creature without flesh, such as an ooze, iron golem, or skeleton, the spell fails.

At Higher Levels. When you cast this spell using a spell slot of 6th-level or higher, both the necrotic and fire damage increase by 1d10 for each slot level above 5th.