Ebony Blade

You concentrate on the shadows around you, drawing them to yourself. They swirl and sway at your command and cloak your currently held weapon, causing it to be wrapped in flame like shadows. 

For the duration, your weapon's damage type becomes necrotic and you may use your spellcasting stat in place of strength or dexterity for the attack and damage rolls.

At 5th level, this spell causes your weapon to deal an additional 1d4 necrotic damage per attack. This damage increases by 1d4 at 11th and 17th level.