Legendary Resistance (4/Day). If Adrian fails a saving throw, he can choose to succeed instead.

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

Unholy Smite. When Adrian hits a creature with a melee weapon attack, he can expend one spell slot to deal necrotic damage to the target, in addition to the weapon’s damage. The extra damage is 2d8 for a 1st-level spell slot, plus 1d8 for each spell level higher than 1st, to a maximum of 5d8. The damage increases by 1d8 if the target is a celestial, to a maximum of 6d8.

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

Necrotic Shroud (1/Long Rest). Adrian can use an action to unleash the divine energy within himself, causing two black, ravenlike, flightless wings to sprout from his back. The instant he transforms, other creatures within 10 feet of him that can see him must each succeed on a DC 18 Charisma saving throw or become frightened of him until the end of his next turn.

The transformation lasts for 1 minute or until he end it as a bonus action. During it, once on each of his turns, Adrian can deal an extra 9 necrotic damage to one target when he deals damage to it with an attack or a spell. 

Spellcasting. Adrian is a 19th-level spellcaster. Its spellcasting ability is Charisma (spell save DC 18, +10 to hit with spell attacks). He 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, haste

4th level (3 slots): banishment, staggering smite, find greater steed

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

Spellcasting(lich). The lich is an 18th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 20, +12 to hit with spell attacks). The lich 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

Multiattack. The death knight makes three longsword attacks, any of which can be replaced by Paralyzing touch (can only do so once per multiattack action).

Longsword. Melee Weapon Attack: +12 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.

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 18 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.

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

Adrian 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. Adrian regains spent legendary actions at the start of his turn.

Cantrip. Adrian casts a cantrip.

Weapon Attack. Adrian attacks once with his longsword.

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

Frightening Gaze (Costs 2 Actions). Adrian fixes its 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 Adrian's gaze for the next 24 hours.

Disrupt Life (Costs 3 Actions). Each non-undead creature within 20 feet of Adrian must make a DC 18 Constitution saving throw against this magic, taking 21 (6d6) necrotic damage on a failed save, or half as much damage on a successful one.