Amphibious. The archipelagore can breathe air and water.

Siege Monster. The leviathan deals double damage to objects and structures.

Multiattack.The archipelagore makes three attacks: two with its claws and one with its bite.

Bite. Melee Weapon Attack: +17 to hit, reach 10 ft., one target. Hite: 26 (3d10 + 10) piercing damage.

Claw. Melee Weapon Attack: +17 to hit, reach 20 ft., one target. Hit: 29 (3d12 + 10) bludgeoning damage, and the target is grappled (escape DC 25). The Archipelagor has two claws, each of which can grapple only one target.

Mutate. When the archipelagore mutates a whirlpool appears in the water sucking up one target for each time the archipelagore has mutated. Each targeted creature is pulled 60 ft. below the water surface.