Alekto

Legendary Resistance (3/Day). If Alekto fails a saving throw, he can choose to succeed instead.

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

Sunlight Sensitivity. While in direct sunlight, Alekto has disadvantage on attack rolls, as well as checks that rely on sight.

Spellcasting. Alekto is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). Alekto has the following wizard spells prepared:

Cantrips (at will): mage hand, prestidigitation, ray of frost

1st level (4 slots): detect magic, magic missile, shield, thunderwave

2nd level (3 slots): acid arrow, detect thoughts, invisibility, mirror image

3rd level (3 slots): animate dead, counterspell, dispel magic, fireball

4th level (3 slots): blight, dimension door

5th level (3 slots): cloudkill, scrying

6th level (1 slot): disintegrate, globe of invulnerability

7th level (1 slot): finger of death, plane shift

8th level (1 slot): dominate monster, power word stun

9th level (1 slot): power word kill

Turn Resistance. Alekto has advantage on saving throws against any effect that turns undead.

Multiattack: Alekto can make two attacks.

Life Drain. Melee Attack: +15 to hit, reach 5ft. (15ft. with sword), one creature. Hit: 42 (8d8+8) necrotic damage.  The target must succeed on a DC 16 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken.  This reduction lasts until the target finishes a long rest.  the target dies if this effect reduces its hit point maximum to 0.

Create Specter.  Alekto targets a humanoid within 10 feet of it that gas been dead for no longer than 1 minute and died violently.  The target's spirit rises as a specter in the space of its corpse of the nearest occupied space.  The specter is under Alekto's control and Alekto can have no more than seven under its control at the same time.

Alekto 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. Alekto regains spent legendary actions at the start of its turn.

Cantrip. Alekto casts a cantrip.

Life Drain. Melee Attack: +15 to hit, reach 5ft. (15ft. with sword), one creature. Hit: 42 (8d8+8) necrotic damage.  The target must succeed on a DC 16 Constitution saving throw or its hit point maximum is reduced by an amount equal to the damage taken.  This reduction lasts until the target finishes a long rest.  the target dies if this effect reduces its hit point maximum to 0.

Frightening Gaze (Costs 2 Actions).  Alekto fixes his gaze on one creature it can see within 10 feet of it. The target must succeed on a DC 18 Wisdom saving throw against this magic or become frightened for 1 minute. The frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a target's saving throw is successful or the effect ends for it, the target is immune to Alekto's gaze for the next 24 hours.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of Alekto must make a DC 20 Constitution saving throw against this magic, taking 27 (8d10) necrotic damage on a failed save, or half as much damage on a successful one.