Leviathan by

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> ## Leviathan
>*Gargantuan Elemental, Chaotic Neutral*
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> - **Armor Class** 20 (natural armor)
> - **Hit Points** 320 
> - **Speed** 40ft **Swim** 120ft
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>|STR|DEX|CON|INT|WIS|CHA|
>|:---:|:---:|:---:|:---:|:---:|:---:|
>|30 (+10)|24 (+7)|30 (+10)|10 (+0)|18 (+4)|17 (+3)|
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> - **Saving Throws** Wisdom +10, Charisma +9
> - **Damage Resistances** non-magical bludgeoning, piercing and slashing damage
> - **Damage Immunities** Acid, Poison
> - **Condition Immunities** All except Sleep
> - **Senses** 120ft Darkvision, 30ft Blindsight
> - **Languages** Common, Aquan, Primordial
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> 
> ***Partial Freeze*** If 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.
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> ***Siege Monster*** Leviathan deals double damage to objects and structures (included in Tidal Wave).
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> ***Frightful Presence*** Each creature of Leviathan’s choice that is within 120 feet of him and aware of it must succeed on a DC 21 WIS saving throw or become frightened for 1 minute. A creature can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success. If a creature's saving throw is successful or the effect ends for it, the creature is immune to the dragon's Frightful Presence for the next 24 hours.
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> ***Spellcasting.*** Leviathan has innate spellcasting ability. Her spellcasting ability is Wisdom (spell save DC18, +10 to hit with spell attacks). She has the following spells prepared:
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> Cantrip (at-will): *Acid Splash, Shape Water*
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> 1st level(4 slots): *Create or Destroy Water, Fog Cloud, Thunderwave*
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> 2nd level(3 slots): *Dragon’s Breath(Cold or Acid), Melf's Acid Arrow*
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> 3rd level(3 slots): *Protection from Energy, Water Walk*
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> 4th level(3 slots): *Conjure Minor Elementals, Control Water, Watery Sphere*
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> 5th level(2 slots): *Conjure Elemental, Maelstrom*
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>***Legendary Resistance 3/Day*** Leviathan can choose to succeed on a saving throw that it fails.
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> ### **Actions**
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> ***Multiattack*** Leviathan makes two attacks: one with its slam and one with its tail.
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> ***Slam.*** Natural Weapon Attack: +16 to hit, reach 20ft, ldl0 + 10 bludgeoning damage + ldl0 acid damage.
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> ***Tail.*** Natural Weapon Attack: + 16 to hit, reach 20ft, ld12 + 10 bludgeoning damage + ld12 acid damage.

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> ***Tsunami***(Recharge 6) While submerged, 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.
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>When the wall appears, all other creatures within its area must each make a DC24 Strength saving throw. A creature takes 6dl0 bludgeoning damage on failed save or half as much damage on a successful one. 
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> At the start of each Leviathan's turns after the wall appears, the wall, along with any other creatures in it, moves 50ft 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 5d10 bludgeoning damage.
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> 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 ldl0. When the wall reaches 0 feet in height, the effect ends.
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> A creature caught in the wall can move by swimming. Because of the force of the wave, though, the creature must make a successful DC24 Strength (Athletics) check to swim at all during that turn.
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> 
> ### **Legendary Actions**
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> Leviathan can take 3 legendary reactions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Leviathan regains spent legendary actions at the start of its turn.
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> ***Slam/Tail***(2 Actions) Leviathan make either a Slam or Tail attack. 
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> ***Move*** Leviathan moves up to its speed.
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> ***Cantrip*** Leviathan can cast a cantrip.
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