Anticipate Future. Abigor gains +3 bonus to his AC against any opponent within range of his telepathy.

Innate Spellcasting. Abigor innate spellcasting ability is wisdom (Spell save is DC 20, +12 to hit with spell attacks). He can innately cast the following spells, requiring no material components:

At will: alter self ( can become Medium when changing his appearance), animate dead, charm person, detect magic, dispel evil and good,  invisibility (self only),

3/day: blight, dispel magic, flame strike, suggestion, wall of fire 

Legendary Resistance (3/day). if Abigor fails a saving throw, he can choose to succeed instead.

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

Magic Weapons. Abigor's weapon attacks are magical.

Mount combat. when Abigor mounts a steed (nightmare) he and the steed gain the evasion trait. the steed also gains +3 to its STR score, +3 AC, and +3 hit dice

Regeneration. Abigor regains 20 hit points at the start of his turn. If he takes cold or radiant damage, this trait doesn't function at the start of his next turn. Abigor dies only if he starts his turn with 0 hit points and doesn't regenerate.

Standard (2/day). Abigor has a magical standard that increases his telepathy to 500ft when held in hand. if the standard is broken or taken from Abigor's possession, he can expend one charge to retrieve and fix the standard. if retrieval is impossible the old standard dissolves and Abigor summons a new one. (standard AC 20, hit-points 50)

Multiattack. Abigor makes two melee attacks: both of which must be made with the same weapon.

Axiomatic Unholy Lance. Melee Weapon Attack: +12 to hit, reach 15 ft., one target. Hit: 19 (2d12 + 6) piercing damage plus 22 (4d10) fire damage. 

Thundering outsider bane Greatsword. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 20 (4d6 + 6) slashing damage plus 10 (3d6) thunder damage. if the target it not from the nine hells Abigor takes the highest value of all damage dice instead of rolling them. 

Place Standard. Abigor drives his standard into the ground declaring victory for the nine hells. this grants all of his allies within 80ft including himself a +3 bonus to all attack rolls and saving thows. This bonus is lost outside the 80ft radios. Abigor's enemys must make a DC 22 charisma save or suffer -3 to all attack rolls and saving throws while within the same radios. (standard AC 20 HP 50)

Teleport. Abigor magically teleports, along with any equipment he is wearing and carrying, up to 120 feet to an unoccupied space he can see.

Uniting Rhetoric (2/day). Abigor gives a call to arms, which causes 1d4+4 bearded devils to appear in unoccupied spaces of his choice within 60 feet of him. the bearded devils roll initiative when they appear. they remain until they die, Abigor dismiss any or all of them, or an hour passes.

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

Taking a stand (Costs 3 Actions). Abigor uses his place standard ability 

Teleport. Amon uses his Teleport action.