Arkham; The Lich King

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

Marshal Undead. Unless Arkham is incapacitated, he and undead creatures of his choice within 60 feet of it have advantage on saving throws against features that turn undead.

Spellcasting. Arkham is a 18th-level spellcaster. His spellcasting ability is Charisma (spell save DC 19, +10 to hit with spell attacks). He has the following paladin or wizard spells prepared:

1st level (4 slots): command, magic missile, searing smite

2nd level (3 slots): hold person, mirror image

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

4th level (3 slots): banishment, blight

5th level (2 slots): destructive wave (necrotic)

6th level (1 slot): globe of invulnerability

7th level (1 slot): finger of death

Multiattack. Arkham makes three longsword attacks.

Longsword. Melee Weapon Attack: +11 to hit, reach 5 ft., one target. Hit: 9 (1d8 + 5) slashing damage, or 10 (1d10 + 5) slashing damage if used with two hands, plus 18 (4d8) necrotic damage.

Hellfire Orb (1/Day). The death knight hurls a magical ball of fire that explodes at a point it can see within 120 feet of it. Each creature in a 20-foot-radius sphere centered on that point must make a DC 18 Dexterity saving throw. The sphere spreads around corners. A creature takes 35 (10d6) fire damage and 35 (10d6) necrotic damage on a failed save, or half as much damage on a successful one.

Parry. The death knight adds 6 to its AC against one melee attack that would hit it. To do so, the death knight must see the attacker and be wielding a melee weapon.

.Disrupt Life (Costs 3 actions). Each non-undead creature within 20 feet of Arkham must make a DC 16 Constitution saving throw against this magic, taking 13 (3d6) necrotic damage on a failed save or half as much damage on a successful one.