Asmodeus

Asmodeus (5e Creature) Large fiend, lawful evil
Armor Class 30 (natural armor) Hit Points 736 (20d20 + 400) Speed 60 ft., fly 120 ft. STR DEX CON INT WIS CHA 29 (+9) 20 (+5) 30 (+10) 30 (+10) 27 (+8) 28 (+9)
Saving Throws Str +18, Con +19, Int +19, Wis +17, Cha +18 Skills Arcana +25, Deception +25, Perception +30, Religion +20, Insight +30, Intimidation +25 Damage Vulnerabilities radiant Damage Resistances acid; lightning; psychic; slashing, piercing, and bludgeoning from nonmagical weapons Damage Immunities fire, poison, necrotic, cold Condition Immunities charmed, deafened, blinded, frightened, poisoned, petrified Senses darkvision 240 ft., truesight 120 ft., passive Perception 32 Languages Common, Abyssal, Celestial, Infernal (can understand all languages, telepathy 1 mile) Challenge 30 (155,000 XP)
Discorporation. When Asmodeus drops to 0 hit points or dies, his body is destroyed but his essence travels back to his domain in the Nine Hells, and he is unable to take physical form for a time. However, if he is killed in his domain of Nessus, this does not happen.
Innate Spellcasting Asmodeus' innate spellcasting ability is Intelligence (Spell save DC 30, +25 to hit). Asmodeus can cast the following spells without needing components or expending a spell slot:
At will: Animate dead, geas (9th level), ice storm (9th level), thunderwave (9th level), fire bolt (max level), chil touch (max level), bestow curse (9th level), fireball (9th level), chain Lightning (9th level), disguise self, identify, blight (6th level), phantasmal force.
4/day each: Blindness/deafness (9th level), enthrall, dispel magic (9th level), counter spell (9th level), slow (unlimited range), hold monster, mass suggestion (9th level), wall of fire, wall of ice, sickening radiance, polymorph.
3/day each: Banishment, phantasmal killer, dominate person (9th level), mental prison, harm, finger of death, forcecage, divine word, greater invisibility, symbol.
2/day each: Feeblemind, dominate monster (9th level), shapechange, imprisonment, meteor swarm, power word kill, true polymorph, mass polymorph.
1/day each. Dark star, true resurrection.
Limited Magic Immunity. Asmodeus is immune to spells of the 6th level or lower, unless he wants to be affected.
Regeneration. Asmodeus regains 30 hit points at the start of his turn as long as he hasn't taken any radiant damage.
Magic Weapons. Asmodeus's weapon attacks are magical.
Legendary Resistance (5/day). If Asmodeus fails a saving throw, he can choose to succeed instead.
Magic Resistance. Asmodeus has advantage on saving throws against magical effects.
Reverie of Nessus As an action, Asmodeus can encase himself in a protective barrier which heals him and stops enemies from attacking him. This barrier acts as a globe of invulnerability. The Reverie of Nessus lasts for three rounds, with a different effect for each one:
In the 1st round, Asmodeus is automatically purged of any unwanted spell effects of conditions. In the 2nd round, Asmodeus is purged of any diseases, poisons, or physical maladies (including lost body parts). In the 3rd round, Asmodeus is healed to full hit points and feels as though they just rested a full day, regaining spells and class abilities accordingly.
ACTIONS
Multiattack. Asmodeus can use his frightful presence. He then makes five attacks with either his Ruby Rod or a slam, and then one with his horns.
Slam. Melee Attack: +14 to hit, reach 10 ft., one target. Hit: 53 (10d8+8) bludgeoning damage.
Ruby Rod. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hit: 51 (8d8 + 15 ) piercing damage.
Ruby Rod. Ranged Weapon Attack: +14 to hit, 150/600 ft., one target. Hit: 50 (9d8 + 10) fire damage or 51 (10d8+6) lightning damage.
Horns Melee Attack: +14 to hit, 4d4 piercing damage. The target must succeed on a DC 20 Charisma saving throw or get poisoned. The target must roll again every day. If they fail the saving throw, they take 3d10 poison damage. If they succeed, they are no longer poisoned.
Frightful Presence. Each creature of Asmodeus’s choice that is within 200 feet of Asmodeus and aware of him must succeed on a DC 30 Wisdom saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, 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 Asmodeus's Frightful Presence.
Innate Spellcasting. As A bonus Action, Asmodeus can innately cast one spell.
Soul Bartering. Asmodeus can grant any humanoid one wish (using the spell wish) in its lifetime on the condition that the PC is bound to him after death. Asmodeus can make minor changes to the wishes if he wants. Asmodeus suffers no harmful effects from this action.
"Now you see me". As a bonus action on his turn, Asmodeus can teleport anywhere within his line of sight or in the nine hells.
Loyalty to the Lord. As a bonus action, if Asmodeus' rod was ever knocked or taken out of his hand, he can instantly teleport it back into his palm

LEGENDARY ACTIONS
The Asmodeus can take 5 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. The Asmodeus regains spent legendary actions at the start of its turn.
Call of the Lord. (Costs 2 Actions) Asmodeus can summon eight creatures (with a challenge rating of 20 or below) who reside within 9 hells.
Chilling Gaze. Asmodeus target one creature within 30 ft., the target makes a Wisdom Save of DC 25 on a failed save target takes 3d10 psychic damage, the target becomes frightened for 30 seconds and gains 1 level of exhaustion. On gaining six levels of exhaustion creature doesn’t die but is dominated by Asmodeus.
Contract Established. Asmodeus on touching a humanoid or a piece of dead humanoid calls its soul back and forms a new adult body for the soul to enter. If the target isn’t willing to do so the spell fails. The body that is formed for the soul is a Tiefling’s body. The soul retains all it’s memories and experiences and is friendly towards Asmodeus (his memories are altered such that it obeys Asmodeus).
Hell's Gate. (Costs 2 Actions) As the King of Hell, Asmodeus has absolute control over all of the gates and portals that lead to Hell, as well as those within Hell. The Lord of the Nine can cause a gate or portal to open, sucking in those within 60 feet into a location in the Nine Hells of Asmodeus' choosing if they fail a Wisdom Save DC 25. The Mouth remains open for 3 rounds. A Hell's Mouth appears as a great, diabolically evil human male face with jagged, chewing teeth. Flames burst from the gaping maw as it attempts to suck in unlucky victims. The gate is two way and remains open for five rounds (suction only during the first round).

Asmodeus's true form was that of a wingless scaled serpent hundreds of miles long. His form's sheer size made it impossible for him to meet and enter into conversations with others. Therefore, he created humanoid-looking avatars. The location of his body was kept secret from everyone, including other devils and everyone who learnt of the truth about his body was killed within a day. Asmodeus never showed himself except through avatars or project image, both in humanoid forms.Asmodeus's avatars looked like a slim, charismatic, red-skinned humanoid over 13 feet (4 meters) tall, with horns on his head and glowing red eyes. Overall, he had charismatic and beautiful looks that captivated people. He always had a perfectly trimmed beard and wore very expensive red and black clothing, which were valuable enough to cover the annual national spending of any nation. However, underneath these expensive garments, the body was wracked with bleeding injuries. While he was in pain, he managed to give the impression of someone unconcerned with the pain the injuries caused him. He could manifest ten avatars at once if needed, allowing him to station one on each layer of Hell if he needed to, with a tenth leftover for managing extraplanar duties. Each of his avatars held a Ruby Rod of Asmodeus.