Chainsaw Crow

Lethe. When the devil's soul count is 0, they have advantage on attack rolls, disadvantage on saving throws, and their Intelligence score becomes 3 (-4). Additionally, the devil must use their movement on each of their turns to move as close as possible to the nearest creature they can sense with their soulsight, and then if they are able, they must use their action to attack and attempt to kill that creature. The devil can't act with any other purpose until they add 1 to their soul count.

Soul Devourer. When the devil reduces a creature who isn't a Construct or an Undead to 0 hit points or deals damage to a dying creature, the creature must make a DC 11 Wisdom saving throw. On a failed save, the devil consumes the creature's soul and adds 1 to the devil's soul count. A creature whose soul is consumed in this way immediately dies, and they can't be restored to life by any means short of a wish spell

Hungering Pursuit. The devil can move through the spaces of Large or smaller creatures as if they were difficult terrain. When the devil enters a creature's space for the first time on the devil's turn, the devil can make a Slash attack against that creature (no action required). Additionally, the devil can end their turn in the space of a creature who is Medium or larger, and that creature can't move while in the devil's space without provoking an opportunity attack.

Devilish Hunger. The devil regenerates 10 hit points at the start of its turn as long as at least 1 creature is under the bleed effect of its Slash attack. This effect is suppressed for one turn when the devil is hit with a critical hit.

Slash. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 19 (3d8+6) slashing damage. On a successful hit, the target must succeed on a DC 16 Constitution saving throw or take 7 (2d6) slashing damage at the start of each of their turns. The devil can burn 1 soul to force a creature to make this saving throw with disadvantage.
The target can repeat this saving throw at the end of each of its turns, ending the effect on a success. Recieving healing from a healer's kit or magical healing also ends this effect.
If a creature bleeds in this way for more than two turns, that creature loses 1 Hit Die. Any Hit Dice lost in this way can only be recovered during a Long Rest.

Tendon Slice. Melee Weapon Attack: +9 to hit, reach 5 ft., one target. Hit: 13 (2d6+ 6) slashing damage, and if the target is a Medium or larger creature, they must succeed on a DC 16 Strength saving throw or be knocked prone.

Vengeful Flight (Costs 1 Soul). When an enemy within 40 feet of the devil deals damage to the devil, the devil can fly up to their speed straight toward them. If the devil ends this movement within 5 feet of the enemy, the devil can make a Slash attack against them, causing the target to bleed without expending an additional Soul.

Chain Lash. Melee Weapon Attack: +9 to hit, reach 15 ft., one target. Hit: 16 (3d6+ 6) slashing damage, and if the target is a creature, they must succeed on a DC 16 Strength saving throw or be pulled up to 10 feet toward the devil.