Kraken

The kraken doesnt require air, sustenance, or sleep.

If the kraken fails a saving throw, it can choose to succeed instead. When it does so, it can use its reaction, if available, to attack with its tentacle.

The kraken has advantage on saving throws against spells and magical effects.

The kraken deals double damage to objects and structures.

Melee Weapon Attack: +18 to hit, reach 5 ft., one target. Hit: 36 (4d12 + 10) piercing damage. If the target is a Huge or smaller creature grappled by the kraken the target is swallowed. A swallowed creature is blinded and restrained its Speed is 0 it has total cover from attacks from outside the kraken and it takes 42 (12d6) acid damage at the start of each of the krakens turns.

While underwater the kraken exudes a cloud of ink in a 90-foot-radius sphere. The ink extends around corners and the area is heavily obscured until the end of the krakens next turn or until a strong current dissipates the cloud. Each non-kraken creature in the area when the cloud appears makes a DC 24 Constitution saving throw. On a failure it takes 27 (5d10) poison damage and is poisoned for 1 minute. On a success it takes half damage. A poisoned creature can repeat the saving throw at the end of each of its turns. ending the effect on a success.

If the kraken is outside and the weather is stormy three lightning bolts crack down from the sky each of which strikes a different target within 120 feet of the kraken. A target makes a DC 24 Dexterity saving throw taking 28 (8d6) lightning damage or half damage on a save.

Over the next 10 minutes storm clouds magically gather. At the end of 10 minutes a storm rages for 1 hour in a 5-mile radius.

The kraken uses Fling.

The kraken ends any magical effect that is restraining it or reducing its movement and then swims up to half its swim speed without provoking opportunity attacks. During this movement, it can fit through gaps as narrow as 10 feet wide without squeezing.

The kraken makes one tentacle attack.

Only one legendary action can be used at a time and only at the end of another creatures turn. It regains spent legendary actions at the start of its turn.