monster

Abyssal Leviathan

CR 26

Gargantuan monstrosity, Unaligned

Reveal Stat Block

Armor Class

Hit Points

615 (30d20 + 300)

Speed

0 ft., swim 80 ft.

str

+10

dex

con

+10

int

-1

wis

cha

Saving Throws CON +18, WIS +12, CHA +10

Damage Resistances cold, fire; bludgeoning, piercing, and slashing from nonmagical attacks

Damage Immunities force, thunder

Condition Immunities frightened, paralyzed, prone

Senses blindsight 240 ft., passive Perception 14

Languages -

Amphibious.The leviathan can breathe air and water.

Aether-Crystal Carapace.Any creature that touches the leviathan or hits it with a melee attack while within 10 feet of it takes 17 (5d6) force damage.

Legendary Resistance (3/Day).If the leviathan fails a saving throw, it can choose to succeed instead.

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

Actions

Multiattack.The leviathan makes three attacks: one with its bite and two with its tail. It can use its Mana-Storm Roar in place of its bite.

Bite.Melee Weapon Attack: +19 to hit, reach 20 ft., one target. Hit: 36 (4d12 + 10) piercing damage plus 26 (4d12) force damage. If the target is a Large or smaller creature, it is swallowed. A swallowed creature is blinded and restrained, has total cover against attacks and other effects outside the leviathan, and takes 35 (10d6) acid damage plus 35 (10d6) force damage at the start of each of the leviathan's turns.

Tail.Melee Weapon Attack: +19 to hit, reach 25 ft., one target. Hit: 28 (4d8 + 10) bludgeoning damage plus 13 (3d8) force damage.

Mana-Storm Roar (Recharge 5-6).The leviathan releases a magical roar that warps reality. Each creature within 120 feet of it must make a DC 26 Constitution saving throw, taking 82 (15d10) force damage on a failed save, or half as much damage on a successful one. Additionally, any active spells of 7th level or lower in the area are immediately dispelled.

Legendary Actions

Tail Attack.The leviathan makes one tail attack.

Aether Surge (Costs 2 Actions).The leviathan releases a pulse of raw aether. Each creature within 60 feet of it must succeed on a DC 26 Strength saving throw or be pushed 40 feet away and knocked prone.

Charybdis Vortex (Costs 3 Actions).The leviathan spins rapidly, creating a massive whirlpool. Each creature in the water within 120 feet of the leviathan must succeed on a DC 26 Strength saving throw or be pulled up to 60 feet toward the leviathan and take 33 (6d10) bludgeoning damage.

Abyssal Leviathan

A gargantuan sea monster mutated by raw aether leaking from the Abyssal Trench. Its scales are hardened like aether-crystals, and its roar can summon localized mana-storms. It is a terrifying threat to any vessel in the Broad Swells, capable of swallowing galleons whole and shattering the foundations of coastal fortresses.

The Abyssal Leviathan is not merely an animal; it is an elemental manifestation of the ocean's fury, warped by the unstable energies of the Aether-Bleed. Its presence creates "Dead Magic Zones" and unpredictable weather patterns for miles around its hunting grounds.

Secret Motivation: The Leviathan is drawn to the "Song of the Trench"—a rhythmic vibration coming from a buried precursor machine at the bottom of the Abyssal Trench. It believes it is protecting the machine, which is actually a terraforming device slowly turning the ocean into a liquid-aether soup.

Adventure Hook: The trade routes between the Eastern and Northern continents have been completely severed. The Gilded Corsairs are offering a king's ransom to anyone who can slay the "King of the Swells" and retrieve a shard of its heart-crystal to power a new generation of floating fortresses.