Talon

Your pointer finger erupts into a disgusting talon of magma and acid, flames dancing happily from its surface and acid bleeding from its razor-sharp edge. While active, all unarmed melee attacks you make are now a melee spell attack, and upon a hit, deal 2d6 fire, acid, and slashing damage. In addition, any creature or object hit with a spell attack are set on fire, if possible, taking 2d4 acid and fire damage at the beginning of their turn, requiring an action to extinguish. In addition, you may use your bonus action to fine the spell while maintaining concentration; fining the spell deals a further 1d6 of each damage type on a spell attack; once you fine a spell you cannot fine it again. 

At Higher Levels. When casting this spell using a spell slot of 5th level or higher, fining the spell adds an additional 1d6 to spell attack damage for each spell slot level used above 4th.