Vesmirith the Covenant

Multiattack. The creature makes three attacks: two Pact Claw attacks and one Ledger Lash.

Pact Claw. Melee Weapon Attack: +13 to hit, reach 10 ft., one target. Hit: 21 (3d8+7) slashing damage plus 13 (3d8) necrotic damage as the wound marks the target with a sigil of debt.

Ledger Lash. Melee Weapon Attack: +13 to hit, reach 20 ft., one target. Hit: 28 (4d10+7) bludgeoning damage, and the target must succeed on a DC 21 Wisdom saving throw or be Bound by Clause for 1 minute. While Bound by Clause the target can take no reactions and automatically fails the first saving throw it makes each round. A creature can repeat the saving throw at the end of each of its turns, ending the effect on a success.

Seal of Oath (Recharge 5-6). Vesmirith inscribes a visible, glowing sigil on a creature it can see within 120 feet. The target must succeed on a DC 21 Charisma saving throw or be contractually marked. While marked, each time the target takes 20 or more damage from a single source, that source instead takes half the damage and the target gains one permanent, non-magical injury (DM's choice) unless the contract is satisfied or broken. A Remove Curse or similar magic ends the mark; extinguishing the sigil also requires a successful dispel magic (DC 21).

Covenant Blast. Ranged Spell Attack: +12 to hit, range 150 ft., one target. Hit: 45 (10d8) necrotic damage. If the target is subject to any written pact or oath (including improvised vows, marriage vows, or signed bargains), the blast instead deals maximum damage and the target is stunned until the end of its next turn.

Clause of Return. When a creature hits Vesmirith with an attack, Vesmirith can cause the attacker to make a DC 21 Intelligence saving throw. On a failed save the attacker is compelled by minor contractual compulsion and must use its reaction, if any, to move up to its speed toward Vesmirith and end its movement adjacent to it. This movement does not provoke opportunity attacks.

Ink Mark. Vesmirith marks one creature it can see within 30 feet. The mark deals 14 (4d6) necrotic damage and grants Vesmirith advantage on its next attack roll against that creature. (Costs 1 Action)

Invoke Clause. Vesmirith forces a creature that can hear it within 60 feet to make a DC 21 Wisdom saving throw or be unable to cast spells until the end of its next turn as words of the contract clog its throat. (Costs 2 Actions)

Enforce. Vesmirith takes a single attack with Pact Claw or Ledger Lash. (Costs 2 Actions)

Bind Ledger (Costs 3 Actions). Vesmirith forces one creature it can see within 60 feet to make a DC 21 Charisma saving throw. On a failed save, the creature is paralyzed for 1 round as invisible bindings tighten. While paralyzed by this effect, the creature's name appears on Vesmirith's ledger and the devil regains 20 hit points.