Another of the spells that can be found in the necromantic spellbook Cryptichronos summons a hungry mist.
4th level necromancy
Casting Time: 1 action
Range: 30 ft.
Components: V, S
Duration: 1 minute
With this spell, you cause a pale, large sized cloud of chilling vapor to form at any desired spot within a 30’ radius. The vapor billows, shifts, and appears almost sentient even though it is not truly alive. It moves at a rate of 30 ft. per round, seeking out and enveloping the nearest life-form within reach of its gaseous tendrils (possibly attacking you if you do not take precautions). Once the spell is cast, you do not need to concentrate upon the magic in order for its effects to persist. You do not have any control over the mist once the spell is cast.
The vapor can flow over 10’ high walls and can seep through even the smallest openings and cracks. It cannot pass through airtight barriers (such as a wall of force or a hermetically sealed door), nor can the mist move across an area of fire. The gas avoids open flames, so a you could conceivably keep the vapor at bay with a torch.
The mist drains blood from any creature caught within its area of effect, doing 3d8 necrotic damage per round. The enveloped creature must make a Constitution saving throw during the first round of damage or else fall down incapacitated, unable to leave the gaseous cloud without help. As the vampire mist feeds, it turns dull red. A creature does not need to breathe the vapors in order for their effects to work.
The mist cannot harm an individual protected by an anti-magic shell, and a gust of wind repels the vapor without dispersing it. Violent winds (such as those created by an air elemental) completely obliterate this gaseous horror, as do extremely hot fires (such as those created by a fireball or flame strike). Vampire mist does not harm fire-based creatures. When the duration of the spell expires, the cloud simply thins out into nothingness.