Leviathan

Gargantuan elemental, Neutral

Armor Class

17

Hit Points

328 (16d20+160)

Speed

walk 40 ft., swim 120 ft.

Saves

Wis +10, Cha +9

Damage Resistances

bludgeoning, piercing, slashing from nonmagical attacks

Damage Immunities

acid, poison

Condition Immunities

exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned

Senses

darkvision 60 ft.

Challenge

20

Legendary Resistance (3/Day)

If the leviathan fails a saving throw, it can choose to succeed instead.

Partial Freeze

If the leviathan takes 50 cold damage or more during a single turn, the leviathan partially freezes; until the end of its next turn, its speeds are reduced to 20 feet, and it makes attack rolls with disadvantage.

Siege Monster

The leviathan deals double damage to objects and structures (included in Tidal Wave).

Water Form

The leviathan can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Actions

Multiattack

The leviathan makes two attacks: one with its slam and one with its tail.

Slam

Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 15 (1d10 + 10) bludgeoning damage plus 5 (1d10) acid damage.

Tail

Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 16 (1d12 + 10) bludgeoning damage plus 6 (1d12) acid damage.

Tidal Wave (Recharge 6)

While submerged, the leviathan magically creates a wall of water centered on itself. The wall is up 250 feet long, up to 250 feet high, and up to 50 feet thick. When the wall appears, all other creatures within its area must each make a DC 24 Strength saving throw. A creature takes 33 (6d10) bludgeoning damage on failed save, or half as much damage on a successful one. At the start of each of the leviathan's turns after the wall appears, the wall, along with any other creatures in it, moves 50 feet away from the leviathan. Any Huge or smaller creature inside the wall or whose space the wall enters when it moves must succeed on a DC 24 Strength saving throw or take 27 (5d10) bludgeoning damage. A creature takes this damage no more than once on a turn. At the end of each turn the wall moves, the wall's height is reduced by 50 feet, and the damage creatures take from the wall on subsequent rounds is reduced by 1d10. When the wall reaches 0 feet in height, the effect ends. A creature caught in the wall can move by swimming. Because of the force of the wave, though, the creature must make a successful DC 24 Strength (Athletics) check to swim at all during that turn.

Legendary actions

Legendary Actions (2/Turn)

The elemental can take 2 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The elemental regains spent legendary actions at the start of its turn.

Slam (Costs 2 Actions)

The leviathan makes one slam attack.

Move

The leviathan moves up to its speed.

Leviathan

Gargantuan elemental, typically neutral

Armor Class

17

Hit Points

328 (16d20 + 160)

Speed

walk 40 ft., swim 120 ft.

Saves

Wis +10, Cha +9

Damage Resistances

bludgeoning, piercing, and slashing from nonmagical attacks

Damage Immunities

acid, poison

Condition Immunities

exhaustion, grappled, paralyzed, petrified, poisoned, prone, restrained, stunned

Senses

darkvision 60 ft.

Languages

Challenge

20

Proficiency Bonus

+6

Legendary Resistance (3/Day)

If the leviathan fails a saving throw, it can choose to succeed instead.

Partial Freeze

If the leviathan takes 50 cold damage or more during a single turn, the leviathan partially freezes; until the end of its next turn, its speeds are reduced to 20 feet, and it makes attack rolls with disadvantage.

Siege Monster

The leviathan deals double damage to objects and structures.

Water Form

The leviathan can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.

Actions

Multiattack

The leviathan makes one Slam attack and one Tail attack.

Slam

Melee Weapon Attack: +14 to hit, reach 20 ft., one target. Hit: 21 (2d12 + 8) bludgeoning damage plus 13 (2d12) acid damage.

Tail

Melee Weapon Attack: +14 to hit, reach 20 ft., one target. Hit: 19 (2d10 + 8) bludgeoning damage plus 10 (3d6) acid damage.

Tidal Wave (Recharge 6)

The leviathan magically creates a wave of water that extends from a point it can see within 120 feet of itself. The wave is up to 250 feet long, up to 250 feet tall, and up to 50 feet wide. Each creature in the wave must make a DC 24 Strength saving throw. On a failed save, a creature takes 45 (7d12) bludgeoning damage and is knocked prone. On a successful save, a creature takes half as much damage and isn't knocked prone. The water spreads out across the ground in all directions, extinguishing unprotected flames in its area and within 250 feet of it, and then it vanishes.

Legendary actions

Legendary Actions (3/Turn)

The leviathan can take 3 legendary actions, choosing from the options below. Only one legendary action can be used at a time and only at the end of another creature's turn. The leviathan regains spent legendary actions at the start of its turn.

Move

The leviathan moves up to its speed.

Slam (Costs 2 Actions)

The leviathan makes one Slam attack.