Blood Bath

A flow of mist shoots forth from the outreached hand of the necromancer, blossoming into an explosion of red, bloody  mist, at a target within range of your choice. This MUST be within line of sight.
The mist will invoke the inner most fears of any target, resulting in both Necrotic and Psychic damage

Each creature in a 20-foot-radius sphere centered on that point must make a WISDOM saving throw. The radius increases by a 5 foot radius per spell level above 4th level. (25' at 4th level, 30 foot radius at 5th level, etc)
A target takes 3D6 Necrotic damage and 5d6 Psychic damage on a failed save, or half as much damage on a successful one.

The bloody mist spreads around corners and attaches to any living creature (willing or not).

A WISDOM save is needed to avoid becoming infected with a disease. On a successful save, the target is immune to the disease effects, for 24 hours.
The target is infected on a failed save and until the disease is cured, the target can’t regain hit points except by magical means, and the target’s hit point maximum decreases by 1D6 every 24 hours.
If the target’s hit point maximum drops to 0 as a result of this disease, the target dies.

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 Necrotic for each slot level above 3rd

SUMMARY:

Damage - 3D6 Necrotic + 5D6 Psychic (half on passed save)
Disease on failed saves (drop 1D6 HP, per 24 hours, till death or cure)
Extended Radius - extra 5' per level above 3rd (4th = 25' radius, 5th = 30' radius)