Devil's Sight. Magical darkness doesn't impede Yafehesh's darkvision.

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

Telepathic Bond. The fiend ignores the range restriction on its telepathy when communicating with a creature it has charmed. The two don't even need to be on the same plane of existence.

Shapechanger. Yafehesh can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Without wings, Yafehesh loses its flying speed. Other than its size and speed, its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.

Empowered Attacks. Yafehesh’s attacks are treated as magical for the purpose of bypassing resistance and immunity to nonmagical weapons.

Illumination. Yafehesh sheds bright light in a 30-foot radius and dim light for an additional 30 feet.

Legendary Resistance (3/Day). If Yafehesh fails a saving throw, he can choose to succeed instead.

Innate Spellcasting. Yafehesh’s innate spellcasting ability is Charisma (spell save DC 20, +12 to hit with spell attacks). She can innately cast the following spells, requiring no material components:

At will: fireball, wall of fire

3/day each: fire storm, haste, teleport

Multiattack. The devil makes three melee attacks: two with its fork and one with its tail. It can use Hurl Flame in place of any melee attack.

Greataxe. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 9 (1d12 + 6) piercing damage.

Infernal Whip. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 8 (2d4 + 3) slashing damage plus 10 (2d10) fire damage.

Tail. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 10 (1d8 + 6) piercing damage. If the target is a creature other than an undead or a construct, it must succeed on a DC 17 Constitution saving throw or lose 10 (3d6) hit points at the start of each of its turns due to an infernal wound. Each time the devil hits the wounded target with this attack, the damage dealt by the wound increases by 10 (3d6). Any creature can take an action to stanch the wound with a successful DC 12 Wisdom (Medicine) check. The wound also closes if the target receives magical healing.

Hurl Flame. Ranged Spell Attack: +7 to hit, range 150 ft., one target. Hit: 14 (4d6) fire damage. If the target is a flammable object that isn't being worn or carried, it also catches fire.

Infernal Charm. One humanoid that Yafehesh can see within 30 feet of it must succeed on a DC 15 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys Yafehesh's verbal or telepathic commands. If the target suffers any harm or receives a suicidal command, it can repeat the saving throw, ending the effect on a success. If the target successfully saves against the effect, or if the effect on it ends, the target is immune to this fiend's Charm for the next 24 hours.

Yafehesh can have only one target charmed at a time. If it charms another, the effect on the previous target ends.

Draining Kiss. Yafehesh kisses a creature charmed by it or a willing creature. The target must make a DC 15 Constitution saving throw against this magic, taking 32 (5d10 + 5) psychic damage on a failed save, or half as much damage on a successful one. The target's hit point maximum is reduced by an amount equal to the damage taken. This reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Etherealness. The fiend magically enters the Ethereal Plane from the Material Plane, or vice versa.