Multiattack

A mirror hag can use its Reconfiguring Curse and make one melee attack.

Bite

Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 21 (4d8 + 3) piercing damage, or 39 (8d8 + 3) piercing damage against a stunned target.

Quarterstaff

Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage.

Reconfiguring Curse

The mirror hag curses a living creature within 60 feet, giving it beastly or hideous features. The target of the reconfiguring curse must succeed on a DC 15 Constitution saving throw or take 1d6 Charisma damage. A successful save renders the target immune to further uses of that hag's curse for 24 hours.