Spellcasting. The Dark Sovereign is a 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 18, +10 to hit with spell attacks).

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

Undead Thralls. When the Dark Sovereign casts animate dead, it can target one additional corpse or pile of bones, creating another zombie or skeleton, as appropriate. Whenever it creates an undead using a necromancy spell, it has additional benefits: the creature’s hit point maximum is increased by an amount equal to the Dark Sovereign’s wizard level, and it adds the Dark Sovereign’s proficiency bonus to its weapon damage rolls.

Multiattack. The Dark Sovereign makes two Staff of Shadows attacks.

Staff of Shadows. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 16 (1d6 + 3 + 3d6) bludgeoning and necrotic damage.

Command Undead (Recharge 5-6). The Dark Sovereign targets one undead creature it can see within 60 feet of it. The target must make a DC 18 Wisdom saving throw. On a failed save, the target must obey the Dark Sovereign’s commands for the next 24 hours or until the Dark Sovereign uses Command Undead again. An undead whose challenge rating is equal to or greater than 6 has an advantage on this saving throw.

Spellcasting: The Dark Sovereign is a 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 18, +10 to hit with spell attacks). The Dark Sovereign has the following wizard spells prepared:

• At will: chill touch, mage hand, prestidigitation, ray of frost
• 1st level (4 slots): mage armor, magic missile, ray of sickness, shield
• 2nd level (3 slots): blindness/deafness, misty step, ray of enfeeblement
• 3rd level (3 slots): animate dead, counterspell, vampiric touch
• 4th level (3 slots): blight, dimension door
• 5th level (3 slots): cloudkill, raise dead
• 6th level (2 slots): circle of death, disintegrate
• 7th level (2 slots): finger of death, teleport
• 8th level (1 slot): power word stun
• 9th level (1 slot): power word kill

Command Undead (Recharge 5-6). The Dark Sovereign targets one undead creature it can see within 60 feet of it. The target must make a DC 18 Wisdom saving throw. On a failed save, the target must obey the Dark Sovereign’s commands for the next 24 hours or until the Dark Sovereign uses Command Undead again. An undead whose challenge rating is equal to or greater than 6 has an advantage on this saving throw.

Shadow Harvest. When the Dark Sovereign kills a creature with necrotic damage, the Dark Sovereign regains 10 (3d6) hit points.

 The Dark Sovereign 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 Dark Sovereign regains spent legendary actions at the start of its turn.

Cantrip (Costs 1 Action). The Dark Sovereign casts a cantrip.

Command Minion (Costs 2 Actions). The Dark Sovereign targets one undead creature it controls and commands it to take an attack action.

Dark Escape (Costs 3 Actions). The Dark Sovereign becomes intangible and moves up to its speed without provoking opportunity attacks. It can move through other creatures and objects as if they were difficult terrain.