Gargantuan Construct, unaligned
Armor Class 17 (natural armor)
Hit Points 279 (18d20+90)
Speed swim +60, walk +10
Challenge 16
Saving Throws cha +4, con +1, int +2, str +1, wis +8
Skills perception +3
Damage Resistances acid, thunder; nonmagic B/P/S attacks
Damage Immunities lightning, poison, psychic
Condition Immunities blinded, charmed, deafened, exhaustion, frightened, paralyzed, petrified, poisoned
Senses truesight 120', passive Perception 13
Languages understands creator's languages but can't speak
Construct Nature. Doesn't require air food drink or sleep.
Impregnable. If subjected to an effect that allows it to make a save to take only half damage it instead takes no damage if it succeeds on the save and only half damage if it fails.
Siege Monster. Double damage to objects/structures.
Multiattack. One Slam and two Claws or four Lightning Bolts.
Claw. Melee Weapon Attack: +13 to hit, 15 ft., one target, 26 (4d8+8) slashing damage. If target is Huge or smaller it is grappled (escape DC 19). Leviathan has two claws each of which can grapple only one target.
Slam. Melee Weapon Attack: +13 to hit, 5 ft., one target, 18 (4d4+8) bludgeoning damage and target: DC 19 Str save or be knocked prone.
Lightning Bolt. Ranged Spell Attack: +8 to hit 150/600' one target 17 (4d6+3) lightning.
Pylon Discharge (Recharge 5-6). Discharges energy surge at a point it can see within 200' of it. Each creature within 30' of that point: 45 (10d8) lightning and is blinded until the end of its next turn (DC 19 Dex half damage not blinded).
Arcane Barrage. Sends arcane energy toward a creature it can see within 120' of it. Target begins to glow with arcane energy and at end of target's next turn: 35 (10d6) radiant (DC 19 Con half). Damage is divided evenly between target and all creatures within 10 ft. of it except leviathan.
Source: Tome of Beasts 3 · OGL/Open