Brittle Undead Treant

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

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

Dry Wood. Any fire damage done to the Brittle Undead Treant causes it to catch flame and takes 1d6 fire damage at the start of its turn. It will burn until it is fully engulfed by water or killed. 

Multiattack. The treant makes two slam attacks.

Slam. Melee Weapon Attack: +5 to hit, reach 5 ft., one target. Hit: 14 (3d6 + 4) bludgeoning damage.

Rock. Ranged Weapon Attack: +5 to hit, range 60/180 ft., one target. Hit: 14 (2d10 + 4) bludgeoning damage.

Strength Drain. Melee Weapon Attack: +5 to hit, reach 5 ft., one creature. Hit: 5 (2d6 + 2) necrotic damage, and the target makes a DC 10 Con save or their Strength score is reduced by 1d4. The target dies if this reduces its Strength to 0. Otherwise, the reduction lasts until the target finishes a short or long rest. recharge 1d6 (5,6)