Corpse Haze

When a creature you can see within 30ft of you dies, you can use your reaction to invigorate the fresh corpse with necrotic energy. The blood (or associated substance) of the creature becomes a swarming haze of crimson, that occupies a 5ft space it can share with other objects or creatures.

When a creature enters the spell’s area for the first time on a turn or starts its turn there, it is engulfed by the crimson swarm that cause searing pain, and it must make a Constitution saving throw. It takes 3d10 necrotic damage on a failed save, or half as much damage on a successful one. Should a creature die to this spells effects, a second swarm spawns with the same properties. 

On each of your turns after you cast this spell, you can use an action to move the haze up to 60 feet in any direction. The swarm disappears and the spell ends if it travels further then 120ft away from you. If there is more then one swarm, you can use the same action to move both individually of each other.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d10 for each slot level above 3rd.