Oni is a Large fiend with lawful evil alignment and Challenge Rating 7 in the 2024 SRD. This stat block includes AC 17, 119 hit points, speeds, traits, and actions.
Multiattack - The oni makes two Claw or Nightmare Ray attacks. It can replace one attack with a use of Spellcasting.
Claw - Melee Attack Roll: +7, reach 10 ft. Hit: 10 (1d12 + 4) Slashing damage plus 9 (2d8) Necrotic damage.
Nightmare Ray - Ranged Attack Roll: +5, range 60 ft. Hit: 9 (2d6 + 2) Psychic damage, and the target has the Frightened condition until the start of the oni’s next turn.
Shape-Shift - The oni shape-shifts into a Small or Medium Humanoid or a Large Giant, or it returns to its true form. Other than its size, its game statistics are the same in each form. Any equipment it is wearing or carrying isn’t transformed.
Spellcasting - The oni casts one of the following spells, requiring no Material components and using Charisma as the spellcasting ability (spell save DC 13):