Armor Class 18 (natural armor)
Hit Points 187 (22d10 + 66)
Speed 30 ft., fly 30 ft., swim 30 ft.
Saving Throws INT +7, WIS +7
Skills Perception +11
Damage Resistances psychic
Senses truesight 120 ft., passive Perception 21
Languages Modron, telepathy 120 ft.
Challenge 11
Axiomatic Mind. The octon can't be compelled to act in a manner contrary to its nature or its instructions.
Combat Ready. The octon has advantage on initiative checks.
Disintegration. If the octon dies, its body disintegrates into dust, leaving behind anything it was carrying.
Multiattack. The octon makes three Tentacle attacks.
Tentacle. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 14 (3d6 + 4) bludgeoning damage plus 9 (2d8) lightning damage.
Whirlwind of Tentacles (Recharge 5–6). The octon rapidly extends and spins its ring of tentacles. Each creature within 20 feet of the octon must succeed on a DC 16 Strength saving throw or be pulled up to 10 feet in a straight line toward the octon. Then, the octon makes two Tentacle attacks against each creature within 10 feet of itself.
MPP, p. 40