Telepathic Bond. Abaddon ignores the range restriction on her telepathy when communicating with her master. The two don't even need to be on the same plane of existence.

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

Sneak Attack. Once per turn, Abaddon deals an extra 14 (4d6) damage when she hits a target with a weapon attack and has advantage on the attack roll, or when the target is within 5 feet of an ally of Abaddon that isn't incapacitated and she doesn't have disadvantage on the attack roll.

Cunning Action. Abaddon can take the dash, disengage, or hide action as a bonus action on each of its turns.

Assassinate. During its first turn, Abaddon has advantage on attack rolls against any creature that hasn't taken a turn. Any hit she scores against a surprised creature is a critical hit.

Evasion. If Abaddon is subjected to an effect that allows her to make a Dexterity saving throw to take only half damage, she instead takes no damage if she succeeds on the saving throw, and only half damage if she fails.

Dagger. Melee Weapon Attack: +6 to hit, reach 5ft (range 20/60), Hit: 5 (1d4 + 3) piercing damage and 9 (3d6) necrotic damage.

Claw (Fiend Form Only). Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 6 (1d6 + 3) slashing damage.

Charm. One humanoid Abaddon can see within 30 feet of her must succeed on a DC 15 Wisdom saving throw or be magically charmed for 1 day. The charmed target obeys her 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 Abaddon's Charm for the next 24 hours.

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

Draining Kiss. Abaddon kisses a creature charmed by her 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. Abaddon magically enters the Ethereal Plane from the Material Plane, or vice versa.

Uncanny Dodge. When an attacker that Abaddon can see hits her with an attack, she can halve the attack's damage against her.