Bound Haunting. Mara's spirit is bound to her domain of dread, The Gallery of the Damned. At the start of her turn, if she is outside the Gallery's walls and not possessing a creature of her bloodline using her Possession action, she must succeed on a DC 15 Charisma saving throw or vanish and reappear in an unoccupied space within the Gallery. If she dies, the Gallery is no longer her prison and characters are free to leave.
Incorporeal Movement. Mara can move through other creatures and objects as if they were difficult terrain. She takes 10 (2d10) force damage if she ends her turn inside an object.
Legendary Resistance (1/encounter). If Mara fails a saving throw, she can choose to succeed instead.
Otherworldly Perception. Mara can sense the presence of any creature within 30 feet of it that is invisible or on the Ethereal Plane. It can pinpoint such a creature that is moving.
Ruthless. Mara has advantage on melee attack rolls against any creature that has used the Help action, restored hit points to another creature, or aided another creature through a feature, such as Bardic Inspiration, or magic, such as the longstrider or aid spells, within the last 1 minute. This trait doesn’t give Mara advantage on melee attack rolls against creatures who have features or traits that passively aid others, such as a paladin’s Aura of Protection or a wolf’s Pack Tactics.
Unusual Nature. Mara doesn't require air, food, drink, or sleep.
If Mara is reduced to 0 hit points, she doesn't die or fall unconscious. She throws down her chisel and Any remaining statues in the gallery explode. Each creature within 5 feet of a statue must succeed on a DC 12 Constitution saving throw or take 3 (1d6) slashing damage as statue shrapnel spreads. Mara regains 100 hit points, becomes invisible, and moves up to twice her speed without provoking opportunity attacks.
Multiattack. Mara makes two attacks with Enfeebling Touch or Gristle Chisel in any combination.
Enfeebling Touch. Melee Weapon Attack: +7 to hit, reach 5 ft., one creature. Hit: 14 (4d6) necrotic damage, and the target’s Strength, Intelligence, or Wisdom score (DM's choice) is reduced by 1d4. The target dies if this reduces its Strength to 0. The target is incapacitated if this reduces its Intelligence or Wisdom to 0. Otherwise, the reduction lasts until the target finishes a short or long rest.
Gristle Chisel. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 8 (2d4+3) slashing damage, and the target has a -1d4 penalty to the next attack roll, saving throw, or ability check it makes before the end of its next turn.
Kinetic Sculpture. Mara creates a 15-ft long, 10-ft wide line rippling pulse. Creatures in the cone must succeed on a DC 15 DEX Save or take 9 (2d8) force damage and be knocked 10 ft away from Mara and fall prone. On a successful save, a creature takes half as much damage and is not knocked prone.
Sculpt Flesh (Recharge 5-6). Mara forces a creature to make a DC 15 Constitution saving throw. If the saving throw fails by 5 or more, the creature is instantly encased in plaster and has the petrified condition. Otherwise, on a failed save, plaster begins to trap the target and it is restrained. The restrained creature must repeat the saving throw at the end of its next turn, becoming petrified on a failure or ending the effect on a success. The petrification lasts for one minute, or until the creature is freed. Another creature can attempt to break through the plaster (DC 10 Athletics check to break) or use restorative magic to end the petrification.
Possession (Recharge 6). One humanoid that the ghost can see within 5 feet of it must succeed on a DC 14 Charisma saving throw or be possessed by the ghost; the ghost then disappears, and the target is incapacitated and loses control of its body. The ghost now controls the body but doesn't deprive the target of awareness. The ghost can't be targeted by any attack, spell, or other effect, except ones that turn undead, and it retains its alignment, Intelligence, Wisdom, Charisma, and immunity to being charmed and frightened. It otherwise uses the possessed target's statistics, but doesn't gain access to the target's knowledge, class features, or proficiencies.
The possession lasts until the body drops to 0 hit points, the ghost ends it as a bonus action, or the ghost is turned or forced out by an effect like the dispel evil and good spell. When the possession ends, the ghost reappears in an unoccupied space within 5 feet of the body. The target is immune to this ghost's Possession for 24 hours after succeeding on the saving throw or after the possession ends.
Stone Protector. This reaction is only usable if Mara is within 5 ft of a sculpture. She animates the sculpture to intercept damage from an incoming attack made within 5 ft of her, reducing the damage she takes by 1d10+3.
Legendary Action Uses: 2. Immediately after another creature's turn, Mara can expend a use to take one of the following actions. Mara regains all expended uses at the start of each of her turns.
False Queen's Command. Mara commands an animated statute to make a melee weapon attack against a creature within 5 feet of it that she can see, using its reaction to do so.
Enamor. Mara causes a creature within 30 feet of her that can see and hear her to make a DC 15 Wisdom Saving Throw. On a failed save, the target is charmed by Mara and must immediately use its reaction, if available, to make a melee weapon attack against a creature hostile to her. The charmed condition lasts until the end of the creature's next turn or until it succeeds on the Wisdom Saving throw.
Harrow. Wisdom Saving Throw: DC 15, one creature Mara can see within 90 feet of herself. Failure: 10 (3d6) Psychic damage, and the target has the Frightened condition for 1 minute. The target may repeat the save at the end of each of its turns, ending the effect on a success. Mara can't take this action again until the start of her next turn.
On Initiative count 20 (losing initiative ties), Mara can take a lair action to cause one of the following effects. She can't use the same effect two rounds in a row:
Mara briefly animates the sculptures in her gallery. Each statue attacks one creature within 5 feet of it, with a +7 bonus to hit and dealing 7 (2d6) bludgeoning damage on a hit. If a Medium or smaller creature takes this damage, it is also grappled (escape DC 15).
The gallery spawns 1d2 additional sculptures. There is a 25% chance that she conjures one of the women whose lives she destroyed (Rugile, Zon, or Sophitia) and that they are hostile to her.