Actions

Multiattack. The oni can make two attacks, either with its naginata or slam attacks.

Naginata. Melee Weapon Attack: +7 to hit, reach 10', one target. Hit: 15 (2d10 + 4) 2d10+4 slashing damage.

Slam. Melee Weapon Attack: +11 to hit, reach 5', one target. Hit: 13 (2d4 + 8) 2d4+8 bludgeoning damage. If the creature is size Large or smaller, it must succeed on a DC 19 Constitution saving throw or be knocked 10' away from the oni.

Change Shape. The oni magically polymorphs into a Small or Medium humanoid, or back into its true form. Other than its size, its statistics are the same in each form. Any equipment it is wearing or carrying isn't transformed but appears appropriately sized to its current form.

Reactions

Hinan no toge (Recharge 5-6). Trigger: The oni is hit with an attack by a creature it can see that is within 60'. Result: The oni causes thorny vines to sprout around the targeted creature, forcing the creature must make a Dexterity saving throw (DC 13). Failure: The targeted creature takes 10 (3d6) piercing damage & is pushed 10' in the direction of the oni's choice. Success: The targeted creature takes half damage.