Blood Mist

You pull the blood from a dying creatures' body and use it as a weapon. 

You can cast this spell as a reaction when a humanoid that you can see within 30 feet of you is killed. When you cast this spell, a red mist seeps from the corpse and fills a 10-foot radius sphere. A strong wind dispels this mist. 

Creatures that enter the mist for the first time or end their turn there must make a Constitution saving throw. On a failure, they take 9 (2d8) poison damage and become poisoned until the end of their next turn. On a success, they take half damage and do not become poisoned. If a poisoned creature fails their save, they take an additional 9 (2d8) necrotic damage.

As a bonus action on each of your turns, you can move the mist up to 10 feet in any direction. 

At higher levels. This spell deals an extra die of damage for every level above 2nd that it is cast.