Blood-flame Blade

As a bonus action, you can coat your blade in blood-flame. The blood-flame disappears after a successful hit.

On a hit, the target takes Fire damage equal to 2d4 plus your spellcasting ability modifier. The target must make a DC 12 Constitution saving throw. On a successful save they have disadvantage on their next save against this spell, and on a failed save they must take 1d10 necrotic damage. The target is immune to this damage if they are undead.

The flaming blade sheds Bright Light in a 5-foot radius and Dim Light for an additional 5 feet.

Using a Higher-Level Spell Slot. The damage increases by 1d4 for each spell slot level above 2.