Child of Mist

Convincing appearance. Once the child of mist has shapechanged to corporeal form, it becomes difficult for the target of the deception to reject the apparition as reality. The target must make a DC 17 charisma saving throw or become charmed by the creature upon first recognizing the form taken by the child of mist.

Dark dependency. Upon exposure to sunlight or to the Daylight, a child of mist must make a DC 16 constitution saving throw. On a failed save, the child of mist evaporates into water vapor, dying. On a successful save, the child of mist takes 30 points of radiant damage, and becomes mechanically frightened of the source of light.

Nightmare bringer. If a creature is brought to 0 hit points by a child of mist, instead of having to make death saving throws, they will enter a deep nightmare of loss. The player will remain in a coma unless they manage to overcome the nightmare, at the DMs discretion. The nightmare can also be broken by casting Dispel Magic or Dispel Evil and Good on the target.

Spellcasting. The child of mist is a 1st-level spellcaster. Its spellcasting ability is CHA (Spell save DC 14, +3 to hit with spell attacks). The child of mist can innately cast the following spells, requiring no material components:
As a bonus action and a cantrip the child of mist can cast the Dancing Lights spell.
The child of mist can adopt one cantrip or 1st level spell that was known by the creature whose form it has taken. The child of mist can cast the 1st level spell up to 3 times.

Corporeal deception. Can only use once. While in mist form, the child of mist magically reads the mind and searches the heart of one creature within 60 feet of it. The effect can penetrate barriers, but 3 feet of wood or dirt, 2 feet of stone, 2 inches of metal, or a thin sheet of lead blocks it. The child of mist can then assume the form of someone the target knew, often a loved one. It then takes on the movement speed of the form it has assumed.

Beckon. The child of mist encourages the target of its deception with words of comfort to approach. The target must win in a contest CHA (Insight) or else move strictly towards the child of mist, using at least half of its movement speed, on its next turn.
The target is not required to move into a space which will cause it obvious and immediate harm (such as walking off a cliff or into a fire, approaching the child of mist does not count). The target rolls with disadvantage if charmed.

Treacherous Strike. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 18 (4d8) psychic damage.