Chain Devil Lord

Diabolical Restoration. If the devil dies outside the Nine Hells, its body disappears in sulfurous smoke, and it gains a new body instantly, reviving with all its Hit Points somewhere in the Nine Hells.

Magic Resistance. The devil has Advantage on saving throws against spells and other magical effects.

Chains of Sweet Suffering. A Creature grappled or restrained by A Chain Devil Lords Chain receive half healing from all sources 

Legendary Resistance (3/Day, or 4/Day in Lair). If the Devil fails a saving throw, it can choose to succeed instead

Multiattack. The devil makes three Chain attacks and uses Conjure Infernal Chain.

Chain. Melee Attack Roll: +11, reach 20 ft. Hit: 11 (2d6 + 6) Slashing damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 17) from one of two chains, and it has the Restrained condition until the grapple ends.

Conjure Infernal Chain. The devil conjures a fiery chain to bind a creature. Dexterity Saving Throw: DC 17, one creature the devil can see within 60 feet. Failure: 9 (2d4 + 6) Fire damage, and the target has the Restrained condition until the end of the devil’s next turn, at which point the chain disappears. If the target is Large or smaller, the devil moves the target up to 30 feet straight toward itself. Success: The chain disappears.

Animate Chains (Recharges 5-6). Up to four chains the devil can see within 60 feet of it magically sprout razor-­edged barbs and animate under the devil's control, provided that the chains aren't being worn or carried.

Each animated chain is an object with AC 20, 20 hit points, resistance to piercing damage, and immunity to psychic and thunder damage. When the devil uses multiattack on its turn, it can use each animated chain to make one additional chain attack. An animated chain can grapple one creature of its own but can't make attacks while grappling. An animated chain reverts to its inanimate state if reduced to 0 hit points or if the devil is incapacitated or dies.

Maelstrom of Suffering (Recharge 5-6)

A swarm of chains fly out in all directions from the Chain Devil Lord and all creatures within 30ft must succeed on a Dexterity saving throw: DC 17 or take 5d6 piercing damage and be restrained until the start of their turn. On a successful save they take half as much damage and are not restrained. The Chain Devil heals for half the damage dealt from this attack.

1/Day: Dominate Person

Prolonged Suffering. The Devil moves a creature that's grappled by themselves or a Animated chain they control 30ft in a direction of their choice

Unnerving Gaze. Trigger: A creature the devil can see starts its turn within 30 feet of the devil and can see the devil. Response—Wisdom Saving Throw: DC 17, the triggering creature. Failure: The target has the Frightened condition until the end of its turn. Success: The target is immune to this devil’s Unnerving Gaze for 24 hours.

Legendary Action Uses: 3 (4 in Lair). Immediately after another creature’s turn, the Chain Devil Lord can expend a use to take one of the following actions. The Devil regains all expended uses at the start of each of its turns.

Commanding Presence. The devil uses Spellcasting to cast Command (level 2 version). The Devil can’t take this action again until the start of its next turn. The devil can't take this action again until the start of its next turn.

Jailers Grasp. The Devil Casts Vortex Warp spell on a target within range. The devil can't take this action again until the start of its next turn.

Silent Penance: The Devil casts the Darkness spell with the effects of the silence spell overlapping. This effect does not require concentration and lasts until the end of the devils next turn. (Fiends can see through this darkness) The Devil cant take this action until the start of its next turn.

Torment. The Devil makes a Chain attack against a creature then gains temporary hit points equal to half the damage dealt.