Armor Class 16 ({@item scale mail|phb})
Hit Points 330 (20d12 + 100)
Speed 50 ft., swim 50 ft.
Saving Throws STR +14, CON +10, WIS +9, CHA +9
Skills Arcana +8, Athletics +14, History +8, Perception +9
Damage Resistances cold
Damage Immunities lightning, thunder
Senses passive Perception 19
Languages Common, Giant
Challenge 13
Amphibious. Hekaton can breathe air and water.
Multiattack. Hekaton makes two broken chain attacks.
Broken Chain. Melee Weapon Attack: +14 to hit, reach 10 ft., one target. Hit: 18 (3d6 + 9) bludgeoning damage.
Ballista. Ranged Weapon Attack: +6 to hit, range 120/480 ft., one target. Hit: 18 (3d10 + 2) piercing damage.
Lightning Strike (Recharge 5–6). Hekaton hurls a magical lightning bolt at a point he can see within 500 feet of it. Each creature within 10 feet of that point must make a DC 17 Dexterity saving throw, taking 54 (12d8) lightning damage on a failed save, or half as much damage on a successful one.
Thunderous Stomp (Recharge 5–6). Hekaton stomps the ground, triggering a thunderclap. All other creatures within 15 feet of him must succeed on a DC 17 Constitution saving throw or take 33 (6d10) thunder damage and be deafened until the start of Hekaton's next turn. On a successful save, a creature takes half as much damage and isn't deafened. The thunderclap can be heard out to a range of 1,200 feet.
SKT, p. 222