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

Spellcasting. Acastes is an 18th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 248, +16 to hit with spell attacks). Acastes 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): wish

Innate Spellcasting. Acastes spellcasting ability is Charisma (spell save DC 25). It can innately cast the following spells, requiring no material components:

At will: detect evil and good, invisibility (self only)

3/day each: blade barrier, dispel evil and good, resurrection

1/day each: commune, control weather

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

Paralyzing Touch. Melee Spell Attack: +12 to hit, reach 5 ft., one creature. Hit: 10 (3d6) cold damage. The target must succeed on a DC 26 Constitution saving throw or be paralyzed for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Multiattack. Acastes makes two greatsword attacks.

Greatsword. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 22 (4d6 + 8) slashing damage plus 27 (6d8) radiant damage.

Longbow. Ranged Weapon Attack: +13 to hit, range 150/600 ft., one target. Hit: 15 (2d8 + 6) piercing damage plus 27 (6d8) radiant damage.

Flying Sword. Acastes releases its greatsword to hover magically in an unoccupied space within 5 feet of it. If Acastes' can see the sword, it can mentally command it as a bonus action to fly up to 50 feet and either make one attack against a target or return to Acastes' hands. If the hovering sword is targeted by any effect, Acastes is considered to be holding it. The hovering sword falls if Acastes dies.

Healing Touch (4/Day). Acastes touches another creature. The target magically regains 40 (8d8 + 4) hit points and is freed from any curse, disease, poison, blindness, or deafness.

Acastes can take 5 legendary actions, choosing from the options below. Only 3 legendary action option can be used at a time and only at the end of another creature's turn. Acastes regains spent legendary actions at the start of every turn.

Cantrip. The lich casts a cantrip.

Paralyzing Touch (Costs 2 Actions). Acastes uses its Paralyzing Touch.

Multiattack(costs 5 actions). Acastes makes either three Greatsword attacks, or one Longbow, and casts one 5th (or lower) spell.