You can grow the gnarled oak of a treant. As a Bonus Action, you can gain the benefits below for 1 minute or until you choose to end them (no action required). Once you use this feature, you can't use it again until you finish a Short or Long Rest.
Armor of Thorns
You gain a +4 bonus to AC. Whenever you take damage from an enemy within 5 feet of you, the enemy takes 4d6 Piercing damage and the AC bonus decreases by 1, to a minimum of +0.
Entangling Transformation
When you use this feature, plants and vines sprout from the ground in a 15-foot Emanation originating from you. Each creature you choose in the Emanation must succeed on a Strength saving throw (DC 8 plus your Constitution modifier plus your Proficiency Bonus) or have the Restrained condition for 1 minute. A Restrained creature can take an action to make a Strength (Athletics) check against this benefit's save DC, ending the condition on itself on a success.