Chromatic edge

You summon arcane energy to form into a dagger in your hand. Choose a damage type from; Cold, Fire, Acid, Poison, Radiant, Necrotic, Thunder or Lightning. This blade is made from this element. The blade will last for 1 minute unless you release your grip on it, in which case it disappears. You can use your action to make a melee weapon attack using the chromatic energy, you use dagger statistics for the attack, but exchange the damage with the chosen elemental type. 

Damage increases by 1d4 at 5th level, and an additional 1d4 at 11th and 17th level.