Argul, Lord of Necromancy

Magic Resistance. Advantage on saving throws against magical spells or effects.

Presence of the Mad. Every 1 hour, all creatures within 60 feet must make a wisdom saving throw, on a fail be frightened for 1 round and take 1d4 psychic damage, otherwise take 1d4 psychic damage.

Siphon. Half of all damage dealt is returned as health.

Spellcasting. The monster can cast any and all Argul spells of 3rd slot and lower as a cantrip. with +4 to attack.

Grasp of Death. Magical black tentacles are summoned from underground that hold a person, the person must make either a strength or dexterity save of DC 18 or higher or get dealt 1d12 damage. The effect lasts until the creature that is being held escapes. Only one can be active at a time.

Argul's Bolt of Hatred. RangedWeapon Attack: +3 to hit, range 30/60 ft., up to 3 targets. Hit: 16 (2d10 + 6) necrotic damage.

Arcana Reflection (3/day). Reflect the spell at half power to the original caster, it is counted as a spell you casted. Afterwards, take 1d6 psychic damage.

Convoy of the Damned (1/day). Summon 15 eyes of the dead that all deal 1d4 damage each to a single target and afterwards explode, dealing an extra 1d4 damage each to any creature within 5ft of them.

if health dropped to 0, activate mythic ability on the next turn:

Soul Explosion (On death). A red mist of destruction explodes from the corpse of Argul, everyone within 120ft of the creature must make a dexterity saving check (DC 18) or suffer 6d12 necrotic damage.