Animate Oak Tree

Inscrutable. The animated oak is immune to any effect that would sense its emotions or read its thoughts, as well as any divination spell that it refuses. Wisdom (Insight) checks made to ascertain the tree's intentions or sincerity have disadvantage.

Magic Weapons. The trees' weapon attacks are magical. 

 Bonus Action: Rooted Nature Heal.  The tree, may, as a bonus action, choose to root itself and heal for 4d6 HP.  This requires the tree to remain rooted for 2 rounds and uses half its movement on the third round to uproot itself.  The tree automatically fails all Dex saves throws while in this mode and cannot use its Legendary Action Root Attack until fully mobile again.

Multiattack. The animated oak makes 4 branch attacks, or two branch attacks and one Aura attack.

Branch. Melee Weapon Attack: +12 to hit, reach 10 ft., one target. Hit: 17 (2d10 + 6) slashing damage.

Petrify (3/Day). The animated oak emits a magical aura. Each time it activates its aura before finishing a long rest, the effect is different, as detailed below. Each creature within 100 feet of the tree  must make a saving throw.

First . Each creature that fails a DC 18 Wisdom saving throw is frightened for 1 minute. A frightened creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Second . Each creature that fails a DC 18 Wisdom saving throw is [Tooltip Not Found] and frightened for 1 minute. A frightened creature is paralyzed and can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.

Third . Each creature makes a DC 18 Constitution saving throw. On a failed save, a creature petrified for 1 minute. 

The animated oak 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 sphinx regains spent legendary actions at the start of its turn.

Launched Branch Attack. The animated oak causes a cloud of acorns to explode from its branches.  All creatures with in 50 ft must make a DC 18 Dexterity saving throw or take 10d6 +15 points of damage.  Successful saving throw take half the damage.

Root Attack (Costs 2 Actions). The animated oak causes it roots to rush through the ground, exploding above the ground targeting up to 4 creatures with in 100 ft of the tree.  Each root attack is rolled as a melee attack.  A successful hit deals 2d6 +6 damage and the target must make a DC 18 strength saving throw or be draw underground and be considered grappled by the tree.

Sap attack (Costs 2 Actions). The tree can target up to 6 creatures within 15 ft of it and cause a stream of sticky sap to spray on to the creature.  To hit +12. On a successful attack, the target must make a DC 18 Strength saving throw or be reduced to half speed and take 4d6 + 10 bludgeoning damage.