Black orbs of necromantic origins which can be used to animate corpses.
The possessed host is worn as a “sleeve” – it takes half their HP in raw tissue damage it can sustain (minimum 15). It cannot sustain a second death – the soul is finally free. In order to achieve this, it attacks everything in sight, in the hopes that it will be killed and sent to its reward. The skin of the creature will turn black (it sheds any armor and clothes – it cannot stand the touch of things), it gains resistance to poison, necrotic, fire, and is immune to cold of all kinds. Its eyes radiate black “light” that can snuff out light sources within 30, 1 per round as a Reaction action. It does not see with sight, so it cannot be blinded.
AC: 13, HP: depends (min. 15), 2 attacks/1 Action; +3 attack, D6/3 +2 damage each. When the creature is killed, the blackened skin peels and lifts in a burst of ashen dust; all within 10′ must make a DC 12 Constitution save or suffer one of the effects of the Contagion spell for 3 rounds.