Freedom of Movement. The kraken ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Multiattack. The kraken makes two tentacle attacks, each of which it can replace with a use of Fling.

Bite. Melee Weapon Attack: +11 to hit, reach 5 ft., 1 target. Hit: 20 (3d8 + 7) piercing damage. 

Tentacle. Melee Weapon Attack: +11 to hit, reach 20 ft., 1 target. Hit: 17 (3d6 + 7) bludgeoning damage, and the target is grappled (escape DC 19). Until the grapple ends, the target is restrained. The kraken has 10 tentacles, each of which can be used to grapple one target.

Fling. One Medium or smaller object or creature held or grappled by the kraken is thrown up to 40 feet in a random direction, and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown.

Grave Bolt. The kraken magically creates a bolt of pure necromantic energy, which can strike a target the kraken can see within 90 feet of it. The target must make a DC 17 Dexterity saving throw. taking 22 (4d10) necrotic damage on a failed save, or half as much on a successful one.

The kraken can take 3 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 (Costs 2 Actions). The kraken makes one tentacle attack.

Fling. The kraken uses Fling.

Death Mist (Costs 3 Actions). The kraken expels dark energy from its body, creating a 40-foot radius of dread and doom. The mist spreads around corners, and that area is heavily obscured to creatures other than the kraken. Each creature in the area other than the kraken that ends its turn there must make a DC 17 Constitution saving throw, taking 16 (3d10) necrotic damage on a failed save, or half as much on a successful one. A strong wind or current can disperse the mist, which otherwise disappears at the end of the kraken's next turn.