Necrichor

The necrichor can move through a space as narrow as 1 inch without expending extra movement to do so.

If the necrichor fails a saving throw, it can choose to succeed instead.

If destroyed, the necrichor revives with all its Hit Points in 1d10 days in the nearest unoccupied space next to a creature of its choice that it has previously possessed with its Blood Puppeteering action. This trait doesn't function if the destroyed necrichor's remains are in a vessel affected by the Hallow spell or if all the necrichor's previous Blood Puppeteering targets are dead.

The necrichor can climb difficult surfaces, including along ceilings, without needing to make an ability check.

The necrichor makes two Necrotic Burst attacks.

Melee or Ranged Attack Roll: +6, reach 5 ft. or range 120 ft. Hit: 12 (2d8 + 3) Force damage plus 11 (2d10) Necrotic damage, and the target has the Poisoned condition until the start of the necrichor's next turn. While Poisoned, the target can't regain Hit Points.

Constitution Saving Throw: DC 15, one Bloodied creature within 5 feet. Constructs and Undead automatically succeed on this save. Failure: The target is possessed by the necrichor; the necrichor disappears, and the target has the Incapacitated condition and loses control of its body. The necrichor now controls the target's body, but the target retains awareness. The necrichor can't be targeted by any attack, spell, or other effect except ones that specifically target Undead. The necrichor's game statistics are the same, except it uses the possessed target's Speed and Strength, Dexterity, and Constitution scores.

The possession lasts until the target drops to 0 Hit Points or the necrichor leaves it as a Bonus Action. When the possession ends, the necrichor appears in an unoccupied space within 5 feet of the target, and the target is immune to this necrichor's Blood Puppeteering for 24 hours. Success: The target is immune to this necrichor's Blood Puppeteering for 24 hours.