Innate Spellcasting. The oni's innate spellcasting ability is Charisma (spell save DC 12). The oni can innately cast the following spells, requiring no material components:

• At will: Darkness, Firebolt, Invisibility
• 1/Day each: Charm Person, Sleep

Chikujō no Oni. When the oni is within 60' of one or more other oni & must make a saving throw, it uses the highest saving throw bonus among the group.

Lethal Momentum. If the oni's weapon attack causes a creature to drop to 0 HP or less, it can make one additional weapon attack.

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

Moeru Karada. The oni's body is wreathed in flame. Creatures take 3 (1d6) 1d6 fire damage at the end of the oni's turn if they are within 5' of it. Furthermore, a creature will take 3 (1d6) 1d6 fire damage if it touches or makes a melee weapon or unarmed attack against the oni. A creature can only take damage from touching or striking the oni once per turn. Other oni are immune to this ability & the oni can temporarily suppress this ability at will.

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

Siege Monster. The oni's attacks do double damage to buildings & objects.