Council of Five.

The ghost has a trait based on who it is, as shown below:

Enezesku: Enfeebling Ray. Enezesku's Innate Spellcasting trait includes ray of enfeeblement, which he can cast at will.
Fautomni: Undead Fortitude. If damage reduces Fautomni to 0 hit points, he must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, Fautomni drops to 1 hit point instead.
Karlov: Unnatural Vigor. When Karlov regains hit points, he has advantage on attack rolls he makes on his next turn.
Vuliev: Teleportation. Vuliev's Innate Spellcasting trait includes misty step, which he can cast at will.
Xil Xaxosz: Lingering Spite. When Xil Xaxosz is reduced to 0 hit points, his incorporeal form explodes in a burst of necrotic energy. Each creature within 5 feet of him must make a DC 16 Constitution saving throw, taking 14 (4d6) necrotic damage on a failed save, or half as much damage on a successful one.

Ethereal Sight.

The ghost can see 60 feet into the Ethereal Plane when it is on the Material Plane, and vice versa.

Incorporeal Movement.

The ghost can move through other creatures and objects as if they were difficult terrain. It takes 5 (1d10) force damage if it ends its turn inside an object.

Innate Spellcasting.

The ghost's innate spellcasting ability is Wisdom (spell save DC 16, +8 to hit with spell attacks). It can innately cast the following spells, requiring no components:

At will: chill touch (at 5th level, and the ghost regains hit points equal to half the amount of damage the target takes)
1/day each: sanctuary, spirit guardians (at 4th level)

Legendary Resistance (1/Day).

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

Actions

Life Drain.

Melee Weapon Attack: +8 to hit, reach 5 ft., one creature. Hit: 18 (4d8) necrotic damage, and the ghost regains hit points equal to half the amount of damage the target takes. The target must succeed on a DC 13 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken. The target dies if its hit point maximum is reduced to 0. This reduction to the target's hit point maximum lasts until the target finishes a long rest.

Convene the Ghost Council.

The ghost summons the other four members of the Obzedat. At the start of the ghost's next turn, the other members appear in unoccupied spaces within 30 feet of the summoner. The ghosts each roll initiative when they appear.

Legendary Actions

If five Obzedat ghosts are all within 30 feet of each other, they can collectively take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time, and only at the end of another creature's turn. Obzedat ghosts regain spent legendary actions at the start of the turn of the ghost with the highest initiative.

Forced Obedience. A target that all of the Obzedat ghosts can see must succeed on a DC 16 Wisdom saving throw or bow until the end of its next turn. Until this bow ends, the target can't take actions or reactions, and its speed is 0 and can't be increased.
Indentured Spirits (Costs 3 Actions). The Obzedat ghosts conjure 1d6 indentured spirits (described in this chapter) within 60 feet of one of them.

Obzedat Ghost