Special Equipment. Zalthar wields a nine lives stealer longsword with 5 charges remaining.

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

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

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

1st level (4 slots): command, compelled duel, searing smite

2nd level (3 slots): hold person, magic weapon

3rd level (3 slots): dispel magic, elemental weapon

4th level (3 slots): locate creature, staggering smite

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

Multiattack. Zalthar makes three longsword attacks.

Nine Lives Stealer Longsword. Melee Weapon Attack: +13 to hit, reach 5 ft., one target. Hit:11 (1d8 + 7) slashing damage, or 12 (1d10 + 7) slashing damage if used with two hands, plus 18 (4d8) necrotic damage.

Hellfire Orb (1/Day). Zalthar 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. Zalthar 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.