Shapechanger. The fiend can use its action to polymorph into a Small or Medium humanoid, or back into its true form. Without wings, the fiend 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.

Multiattack. The Zuccubus makes two Zucc'ening attacks. One or both of these attacks can be replaced with either Humiliating Memory or Book of Faces.

Zucc'ening. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 8 (1d6 + 5) piercing damage.

Humiliating Memory. One humanoid the fiend can see within 30 feet of it must succeed on a DC 15 Wisdom saving throw or be magically stunned by the horrors of its past for 1 minute. The stunned target can repeat the saving throw and the end of each of its turns, ending the effect on a success. 

Book of Faces. The fiend chooses a creature either stunned by it. 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. If the damage reduces the target to 0 HP, the Zuccubus peels the face off the creature, adding it to its ever growing collection.

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

Deflect Blame. If the Zuccubus is the target of a ranged attack, it may use its reaction to redirect the attack to one creature within 5 ft. of it.

Privacy Reforms. When the Zuccubus is hit with an attack, it may use its reaction to increase its AC by 3 until the beginning of its next turn.