Blood Bolt

You fire a hot, boiling bolt of blood at a creature you can see. Make an attack roll, and on a hit deal 3D12 Necrotic damage and 3D6 Fire damage, and an additional 3D6 Fire damage to the affected entity over the next 3 turns. Apply the DoT effects at the start of the enemy’s next turn(s). 

Upcasting increases the initial Necrotic and fire damage by a D12 and D6 respectively, and increases the DoT effects by a D6 per spell slot level after third.