Innate Spellcasting. The hag's innate spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). She can innately cast the following spells, requiring no material components:

At will: detect magic, magic missile

2/day each: plane shift (self only), ray of enfeeblement, sleep

1st level (4 slots): identify, ray of sickness

2nd level (3 slots): hold person, locate object

3rd level (3 slots): bestow curse, counterspell, lightning bolt

4th level (3 slots): phantasmal killer, polymorph

5th level (2 slots): contact other plane, scrying, dream

6th level (2 slot): eyebite

7th level (1 slot): Prismatic Spray

8th level (1 slot): Abi-Dalzim's Horrid Wilting

Magic Resistance. The hag has advantage on saving throws against spells and other magical effects.

Spider Climb. climb walls and walk across ceilings as if they were normal terrain and suffers no penalty to her speed in doing so.

Legendary Resistance (2/Day). If the night hag fails a saving throw, it can choose to succeed instead.

Claws.(Hag Form Only). Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 13 (4d8 + 5) slashing damage.

Change Shape. The hag magically polymorphs into a Small or Medium female humanoid, or back into her true form. Her statistics are the same in each form. Any equipment she is wearing or carrying isn't transformed. She reverts to her true form if she dies.

Etherealness. The hag magically enters the Ethereal Plane from the Material Plane, or vice versa. To do so, the hag must have a heartstone in her possession.

Nightmare Haunting (1/Day). While on the Ethereal Plane, the hag magically touches a sleeping humanoid on the Material Plane. A protection from evil and good spell cast on the target prevents this contact, as does a magic circle. As long as the contact persists, the target has dreadful visions. If these visions last for at least 1 hour, the target gains no benefit from its rest, and its hit point maximum is reduced by 5 (1d10). If this effect reduces the target's hit point maximum to 0, the target dies, and if the target was evil, its soul is trapped in the hag's soul bag. The reduction to the target's hit point maximum lasts until removed by the greater restoration spell or similar magic.

The night hag can 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. The night hag regains spent legendary actions at the start of its turn.

Bead of Darkness. Yskra throws a bead to the floor that explodes into a 20 foot sphere of magical darkness.

Ethereal Shift. The Night Hag shifts into the ethereal plane and moves of to her movement away. this does not provoke opportunity attacks.

Spellcasting: Yskra can cast one spell of 4th level or lower.

Create Undead (Costs 2 Actions). Yskra raises two copses to undeath within the chamber. These creatures are made form the bodies of the Dolikari Goliaths.
These have the stats of a blood zombie (Homebrew)