Black Flame’s Smite

Coat a melee weapon you are holding in pitch black flames which neither emit nor reflect any light. The next time you hit a creature with the enchanted weapon during the spell’s duration, the creature takes an additional 1d8 fire damage, plus 1d4 fire damage for every 25 points of maximum hp it has. This damage ignores resistance to fire damage, and treats immunity like resistance. 

When you cast this spell with a spell slot of 2nd level or higher, deal an additional 1d8 fire damage for each spell level beyond the 1st.