Armor Class 17 ({@item half plate armor|phb})
Hit Points 105 (10d10 + 50)
Speed 30 ft., climb 30 ft.
Saving Throws DEX +7, CON +9, WIS +6
Skills Perception +10, Stealth +11, Survival +10
Damage Resistances cold, [object Object]
Damage Immunities fire, poison
Condition Immunities charmed, exhaustion, poisoned
Senses darkvision 120 ft., truesight 30 ft., passive Perception 20
Languages Common, Infernal, telepathy 120 ft.
Challenge 10
Invisibility Field. The orthon can use a bonus action to become invisible. Any equipment the orthon wears or carries is also invisible as long as the equipment is on its person. This invisibility ends immediately after the orthon makes an attack roll or is hit by an attack.
Magic Resistance. The orthon has advantage on saving throws against spells and other magical effects.
Infernal Dagger. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 11 (2d4 + 6) slashing damage, and the target must make a DC 17 Constitution saving throw, taking 22 (4d10) poison damage on a failed save, or half as much damage on a successful one. On a failure, the target is poisoned for 1 minute. The poisoned target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Brass Crossbow. Ranged Weapon Attack: +7 to hit, range 100/400 ft., one target. Hit: 14 (2d10 + 3) piercing damage, plus one of the following effects:
Explosive Retribution. When it is reduced to 15 hit points or fewer, the orthon causes itself to explode. All other creatures within 30 feet of it must each make a DC 17 Dexterity saving throw, taking 9 (2d8) fire damage plus 9 (2d8) thunder damage on a failed save, or half as much damage on a successful one. This explosion destroys the orthon, its infernal dagger, and its brass crossbow.
Mordenkainen's Tome of Foes, p. 169