Death Mark

You gather waves of angry magic and force it into a target you can see within 60ft of you. While the mark is active you and up to 5 creatures you choose deal an extra 1D6 necrotic damage to the foe and once that foe has fallen the target explodes in blood and magic dealing 3D10 necrotic damage in a 5ft radius and passing the ailment on to any creatures in the blast zone causing secondary explosions when their moment of reaping comes.