Valdrik The Undying

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

Turn immunity. Valdrik is immune to turn dead affects.

Age fighter. Valdric crits on 19 & 20.

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

Challenging Stare. When making eye contact, Valdrik can force a enemy to make a DC 25 Wisdom save, if failed the enemy is forced to either move closer or attack valdrik and cannot do anything else untill the save is succeeded. 

Spellcasting. Valdrik is capable of 19th-level spellcasting. 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, searing smite

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

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

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

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

Undying Nature. If valdrik is reduced to 0 hp he is set back to 700 hp but is Stunned for 1 minute

Dark ties. all deck of many things cards are temporary converted to the SKULL card while within 120ft of him

Mythic trait: ends if valdrik is reduced to 0 hp. Valdrik absorbs a nearby Avatar of Death to gain its mythic traits as aditional legendary actions.

Multiattack. The death knight makes three longsword attacks.

Longsword. Melee Weapon Attack: +11 to hit, reach 10 ft., one target. Hit: 12 (2d8 + 5) slashing damage, or 15 (2d10 + 5) slashing damage if used with two hands, plus 18 (4d8) necrotic damage.

Valdrikcan 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. Valdrik regains spent legendary actions at the start of its turn

Marked for Death. Valdrik can mark a single enemy for death, this will cause the next attack to hit deal double damage

Ethereal Pull. Valdrik can pull any enemy in the ethereal plane within "120ft" 60ft closer, if the enemy becomes within attack range of valdrik he can then make an attack against them. if a enemy is occupying the same space on the material plane as the ethereal enemy he makes attack roll against both targets.

 Death March. Valdric moves up to its speed.

Cruel Example, Valdrik raises a dead enemy from the grave and then strikes it down once again, all allies previous of the raised dead within sight must make a DC 20 wisdom save or be frighten for 1 minute, in addtion all allies of raised dead take 10D10 psychic damage or half damage on save.

No Escape. Valdrik forms Wings of darkness and gains a fly speed of 50 ft.

Command the Dead. all undead creatures within 120ft become under valdriks control