Bound Oni

Regeneration. The oni regains 10 hit points at the start of its turn if it has at least 1 hit point.

Magic Weapons. The oni's weapon attacks are magical.

Innate Spellcasting. The oni's innate spellcasting ability is Charisma (spell save DC 13). The oni can innately cast the following spells, requiring no material components:

• At will: darkness, invisibility
• 1/day each: charm person, cone of cold, gaseous form, sleep

Multiattack. The oni makes two attacks, either with its claws or its glaive.

Claw. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) slashing damage.

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

Change Shape. The oni magically polymorphs into a Small or Medium humanoid, into a Large giant, or back into its true form. Its statistics, other than its size, are the same in each form. Any equipment it is wearing or carrying isn't transformed. It reverts to its true form if it dies.