Draining Roots. While the treant is on the ground, each non-undead creature that starts its turn on the ground within 60 feet of the treant takes 11 (2d10) necrotic damage. If the creature has blood or is a plant, the treant also regains hit points equal to half the damage dealt. This damage is rolled twice against prone creatures and the higher result is used. The treant can disable or enable this trait as a bonus action.

False Appearance. While the treant remains motionless, it is indistinguishable from a normal dead tree.

Hellflame Tinder. Whenever the treant takes fire damage, it burns with unholy flame until the end of its next turn. While burning, the treant sheds bright light for 30 feet and dim light for an additional 30 feet, the treant's attacks deal 10 (3d6) extra fire damage on a hit, and any creature within 5 feet of the treant that ends its turn, touches the treant, or hits it with a melee attack takes 10 (3d6) fire damage.

Legendary Resistance (3/Day). If the treant fails a saving throw, it can choose to succeed instead.

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

Siege Monster. The treant deals double damage to objects and structures.

Sunlight Hypersensitivity. The treant takes 20 radiant damage when it starts its turn in sunlight. While in sunlight, it has disadvantage on attack rolls and ability checks.

Turn Defiance. The treant and any undead creatures within 60 feet of it have advantage on saving throws against any effect that turns undead.

Undead Hybrid. The treant is also an undead.

Multiattack. The treant can use its Reanimate Trees action. It then makes two slam attacks or two rock attacks.

Slam. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 22 (4d6 + 8) bludgeoning damage plus 16 (3d10) necrotic damage, and if the target is Medium or smaller, it is grappled (escape DC 20) and restrained until the grapple ends. If the target isn't an undead or construct and has blood, its hit point maximum is reduced by an amount equal to the necrotic damage taken, and the treant regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0.

Rock. Ranged Weapon Attack: +14 to hit, range 60/180 ft., one target. Hit: 35 (5d10 + 8) bludgeoning damage. If the target is a creature, it must succeed on a DC 20 Strength saving throw or else it is knocked prone.

Reanimate Trees (3/Day). The treant magically reanimates one or two dead trees it can see within 60 feet of it. These trees have the same statistics as a rotwood treant, except they have Intelligence and Charisma scores of 1, they can't speak, and they have only the Slam action option. A reanimated tree acts as an ally of the treant. The tree remains reanimated for 1 day or until it dies; until the treant dies or is more than 120 feet from the tree; until it uses this action again; or until the treant takes a bonus action to turn it back into a dead tree.

The treant can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The treant regains spent legendary actions at the start of its turn.

Detect. The treant makes an Intelligence (Arcana) check, an Intelligence (Nature) check, a Wisdom (Insight) check, or a Wisdom (Perception) check.

Heal Blight or Bone. The treant restores up to 20 hit points to one plant or undead that it can see within 60 feet. If the target is an undead other than the treant, the target also gains resistance to radiant damage and can ignore the effects of sunlight until the end of its next turn.

Poison Mist. The treant creates a cloud of toxic mist. It fills a 15-foot sphere centered on a location the treant can see within 120 feet of it and lasts until the end of its next turn. The area is lightly obscured. Any creature that starts its turn in a poison cloud must succeed on a DC 20 Constitution saving throw or else take 19 (3d12) poison damage.

Charm (Costs 2 Actions). The treant targets one humanoid it can see within 60 feet of it. If the target can see the treant, it must succeed on a DC 20 Wisdom saving throw or be charmed by the treant until the end of the treant's next turn. On the charmed target's turn, the treant decides how the creature takes its turn, including its actions and movement.

Hurl Rock (Costs 2 Actions). The treant makes a rock attack.