Gargantuan elemental, neutral

Armor Class: 17 (natural armor)

Hit Points: 328 (16d20 + 160) 16d20+160

Speed: 40 ft , swim: 120 ft

STR

30 +10

DEX

24 +7

CON

30 +10

INT

2 -4

WIS

18 +4

CHA

17 +3

Saving Throws: 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., passive Perception 14

Languages: -

Challenge Rating: 20

Aesi, Tyrant of Gyre Strait by Viktor Titov

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) 1d10+10 bludgeoning damage plus 5 (1d10) 1d10 acid damage.   Tail. Melee Weapon Attack: +16 to hit, reach 20 ft., one target. Hit: 16 (1d12 + 10) 1d12+10 bludgeoning damage plus 6 (1d12) 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) 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) 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

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.   Slam (Costs 2 Actions). The leviathan makes one slam attack.   Move. The leviathan moves up to its speed.

Suggested Environments

Environments. Coastal, Underwater