Corrupted Treant

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

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

Multiattack. The treant makes two slam attacks .

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 21 (3d6 + 6) bludgeoning damage.

Rock. Ranged Weapon Attack: +8 to hit, range 60 ft., one target. Hit: 28 (4d10 + 6) bludgeoning damage.

Animate Trees (1/Day). The treant magically animates one or two trees it can see within 40 feet of it. These trees have the same statistics as a treant, except they have Intelligence and Charisma scores of 1, they can't speak, and they have only the Slam action option. An animated tree acts as an ally of the treant. The tree remains animate for 1 day or until it dies; until the treant dies or is more than 60 feet from the tree; or until the treant takes a bonus action to turn it back into an inanimate tree. The tree then takes root if possible.

Grasping roots (1/Day). The Corrupt Treant releases grasping roots from itself in a 30ft. radius around it . The area is considered difficult terrain,the Treant is not affected by it.
The targets must succeed DC18 DEX. Saving throw or be restrained ,if the targets fails the saving throw they take 13 
(3d6) necrotic damage. They can repeat the saving throw at the start of their turn and if they end their turn inside the area,they take the damage again.