Cozduzeeph the Archlich

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

Death Burst. When a creature under Cozduzeeph's command is reduced to 0 hit points, it explodes in a burst of necrotic energy. Each creature within 5 feet of the creature must make a Dexterity saving throw, taking 27 (6d8) necrotic damage on a failed save or half damage on a success.

Reanimating Presence. If a humanoid dies within 60 feet of Cozduzeeph, it rises at the start of Cozduzeeph next turn as a zombie under its control. If the humanoid's body was protected against rising or was too heavily damaged before being raised, such as through the disintegrate spell, the gentle repose spell, or decapitation, the rising fails.

Rejuvenation. If it has a phylactery, Cozduzeeph gains a new body in 1d4 days, regaining all its hit points and becoming active again. The new body appears within 5 feet of the phylactery.

Spell Mastery. Cozduzeeph can cast magic missile and mirror image at their lowest level without expending a spell slot, and may add its Intelligence modifier to any damage dealt by a spell.

Turn Immunity. Cozduzeeph is immune to effects that turn undead.

Magic Resistance. Cozduzeeph has advantage on saving throws against spells and other magical effects (due to it wearing the Robes and Staff of the Archmagi).

Staff of the Magi. Cozduzeeph has a +2 bonus to spell Attack rolls (already considered). 

The staff has 50 Charges for the following properties. It regains all its Charges daily at dawn.

Cozduzeeph can use an action to expend some of the staff Charges to cast one of the following Spells, its spellcasting ability is Intelligence (spell save DC 26, +20 to hit with spell attacks): Conjure Elemental (7 charges), Dispel Magic (3 charges), Fireball (7th-level version, 7 charges), Flaming Sphere (2 charges), Ice Storm (4 charges), Invisibility (2 charges), Knock (2 charges), Lightning Bolt (7th-level version, 7 charges), Passwall (5 charges), Plane Shift (7 charges), Telekinesis (5 charges), or Wall of Fire (4 charges).

Robes of the Archmagi. Cozduzeeph spell save DC increases by 2(already considered).

Spellcasting. Cozduzeeph is a 20th-level spellcaster. Its spellcasting ability is Intelligence (spell save DC 26, +20 to hit with spell attacks). Cozduzeeph has the following wizard spells prepared:

Multiattack. Cozduzeeph can use its Frightful Presence, and then casts 2 spells with a casting time of 1 action, one of 1st level or higher and one cantrip (can be from its spell slots or from the Staff of Magi). It then makes an attack with its paralyzing touch.

Paralyzing Touch. Melee Weapon Attack: +20 to hit, reach 5 ft., one creature. Hit: 18 (4d8) cold damage. The target must succeed on a DC 20 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 itself on a success.

Frightful Presence. Each creature of Cozduzeeph's choice within 120 feet of it and aware of it must succeed on a DC 18 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, with disadvantage if Cozduzeeph is within line of sight, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to Cozduzeeph's Frightful Presence for the next 24 hours.

Retributive Strike. Cozduzeeph breaks the staff over his knee or against a solid surface, performing a retributive strike. The Staff of Magi is destroyed and releases its remaining magic in an explosion that expands to fill a 30-foot-radius Sphere centered on it.
Cozduzeeph has a 50 percent chance to instantly Travel to a random plane of existence, avoiding the explosion. If Cozduzeeph fails to avoid the effect, he takes force damage equal to 16 x the number of Charges in the staff. Every other creature in the area must make a DC 17 Dexterity saving throw. On a failed save, a creature takes an amount of damage based on how far away it is from the point of Origin, as shown in the following table. On a successful save, a creature takes half as much damage.

Distance from Origin — Damage:

10 ft. away or closer — 8 x the number of Charges in the staff

11 to 20 ft. away — 6 x the number of Charges in the staff

21 to 30 ft. away — 4 x the number of Charges in the staff

Spell Absorption. Cozduzeeph can use his Reaction when another creature casts a spell that Targets only him. If he does, the staff absorbs the magic of the spell, canceling its effect and gaining a number of Charges equal to the absorbed spell's level. However, if doing so brings the staff's total number of Charges above 50, the staff explodes as if retributive strike had been activated.

Cozduzeeph 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. Cozduzeeph regains spent legendary actions at the start of its turn.

Paralyzing Touch. Cozduzeeph uses its Paralyzing Touch.

Sacrifice. Cozduzeeph reduces a creature under its control to 0 hit points, and regains 2d10 + 20 hit points.

Disrupt Life (Costs 2 Actions). Each creature within 20 feet of Cozduzeeph must make a DC 20 Constitution saving throw against this magic, taking 54 (12d8) necrotic damage on a failed save, or half as much damage on a successful one.