Curse of Strahd Kraken

Amphibious. The kraken can breathe air and water.

Colossal. Due to the Kraken's immense size it cannot be moved against it's will.

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

Tentacles. The Kraken has 10 tentacles. No tentacle may be moved more than 60ft from the Kraken by any means. Each tentacle may be attacked separately. They each have an ac of 15 and 25hp. A Tentacle that drops to 0 hp dies. 

When a tentacle dies, The Kraken loses one of it's legendary actions permanently. If the Kraken has been reduced to 0 legendary actions, then it may only make attacks with tentacles that remain when it attacks.

Epic Resistance. When the Kraken fails a saving throw, it may choose to succeed instead. When it does so, one tentacle of the Kraken's choice falls to 0 HP and dies. If its mythic trait is active, the Kraken may sacrifice a mythic tentacle this way.

Epic Fortitude. When the Kraken takes damage that would reduce it to 0 HP, it interposes a tentacle to avoid the damage. The tentacle takes the damage instead of the Kraken.

Area of Affect Resistance. Tentacles are considered to be the same creature as the Kraken. Because of this, whenever the Kraken takes area of effect damage, the kraken can choose to take this damage or have one and only one of it's tentacles in the affected area to take this damage. 

Multiattack. The kraken may move all of it's tentacles up to 60 ft tentacle attacks, it then makes two tentacle attack, each of which it can replace with one use of Fling. The Kraken may also do one Bite attack. A creature grappled by a tentacle moves with the tentacle.

Bite. Melee Weapon Attack: +10 to hit, reach 5 ft., one target. Hit: 23 (2d6+6) piercing damage. If the target is a Large or smaller creature grappled by the kraken, that creature is swallowed, and the grapple ends. While swallowed, the creature is blinded and restrained, it has total cover against attacks and other effects outside the kraken, and it takes 21 (6d6) acid damage at the start of each of the kraken's turns.

If the kraken takes 25 damage or more on a single turn from a creature inside it, the kraken must succeed on a DC 22 Constitution saving throw at the end of that turn or regurgitate all swallowed creatures, which fall prone in a space within 10 feet of the kraken. If the kraken dies, a swallowed creature is no longer restrained by it and can escape from the corpse using 15 feet of movement, exiting prone.

Tentacle. Melee Weapon Attack: +10 to hit, reach 30 ft., one target. Hit: 10 (1d6 + 6) bludgeoning damage, and the target is grappled (escape DC 15). Until this grapple ends, the target is restrained. The kraken has ten tentacles, each of which can grapple one target.

Fling. One Large or smaller object held or creature grappled by the kraken is thrown up to 60 feet in a direction of the Kraken's choice and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (3d6) bludgeoning damage. If the target is thrown at another creature, that creature must succeed on a DC 15 Dexterity saving throw or take the same damage and be knocked prone.

Lightning Strike. The kraken magically creates one bolt of lightning, which can strike a 5ft radius (2x2 square) the kraken can see within 120 feet of it. A target must make a DC 18 Dexterity saving throw, taking 17 (3d10) lightning damage on a failed save, or half as much damage on a successful one. Objects of magical force in the area are destroyed.

The kraken can take 8 legendary actions, 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. The kraken regains spent legendary actions at the start of its turn.

Tentacle Attack or Fling. The kraken makes one tentacle attack or uses its Fling. The Kraken may only take this action with a tentacle that hasn't acted since the start of the kraken's turn.

Lightning Strike (Costs 3 Actions). The kraken uses Lightning Strike.

Ink Cloud (Costs 3 Actions). While underwater, the kraken expels an ink cloud in a 60-foot radius. The cloud spreads around corners, and that area is heavily obscured to creatures other than the kraken. Each creature other than the kraken that ends its turn there must succeed on a DC 18 Constitution saving throw, taking 9 (2d8) poison damage on a failed save, or half as much damage on a successful one. A strong current disperses the cloud, which otherwise disappears at the end of the kraken's next turn.

Unnatural Existence (Mythic Trait; Recharges after a Short or Long Rest.)

When the Kraken is reduced to 0 hit points, it doesn't die or fall unconscious. Instead, it's armor plating cracks and from those cracks two, rotting putrid looking tentacles sprout. The kraken gains immunity to necrotic and poison damage. Each putrid tentacle sprouts within 10 feet of the kraken. They each have an ac of 18 and have 105 hp. When both putrid tentacles die, the Kraken dies. The Kraken gains two legendary Actions. when a mythic tentacle dies, the Kraken loses on of these actions. Putrid tentacles deal an extra 2d6 necrotic damage.