Chaos Strike

When you hit a creature with a melee weapon attack, you can expend one spell slot to deal fire damage to the target, in addition to the weapon's damage.

The bonus damage is 2d8 for a 1st level spell slot.

The damage increases by 1d8 against fey, fiends, and celestials.

At higher levels:

The damage increases by 1d8 for each slot above 1st