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

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

Stench. Any non-undead creature that starts its turn within 15 feet of the treant must succeed on a DC 16 Constitution saving throw or be poisoned until the start of the creature's next turn. On a successful saving throw, the creature is immune to the stench of all rotwood treants for 1 hour. Whenever the treant takes fire damage, until the end of its next turn, the range of this trait increases from 15 feet to 60 feet and creatures have disadvantage on the saving throw.

Sunlight Sensitivity. While in sunlight, the treant has disadvantage on attack rolls, as well as on Wisdom (Perception) checks that rely on sight.

Undead Hybrid. The treant is also an undead.

Multiattack. The treant makes two slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 16 (3d6 + 6) bludgeoning damage plus 9 (2d8) poison damage.

Rock. Ranged Weapon Attack: +10 to hit, range 60/180 ft., one target. Hit: 28 (4d10 + 6) bludgeoning damage plus 13 (3d8) poison damage.
    On a hit or a miss, the attack also creates a cloud of foul stench that fills a 15-foot sphere centered on the target. The cloud lasts for 1 minute or until a wind of moderate or greater speed (at least 10 miles per hour) disperses it. Each creature that starts its turn in the area is affected by the treant's Stench trait.

Reanimate Trees (1/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 normal treant, except they have Intelligence and Charisma scores of 1, they're undead, they can't speak, and they have only the Slam action option, but they also have resistance to necrotic and poison damage and they have the treant's Stench and False Appearance traits. A reanimated tree acts as an ally of the treant. A tree remains reanimated for 1 day or until it dies; until the treant dies or is more than 120 feet from the tree; or until the treant uses a bonus action to turn it back into a dead tree.