Elder Terrors.

In the deepest parts of the world, long forgotten by the mortals of the surface these terrors of a prior age scheme and plot. Sheltered by the cold of sunless seas and crushing depths they wait for the perfect time for their revenge. The pressure of the chasms where these being dwell have forged the eldritch kraken into a far hardier specimen than their smaller brethren.

Forgotten Rituals. Using monstrous rituals consuming incalculable sacrifices some elder krakens managed to gain even greater power becoming the first eldritch krakens. It even managed to allow these ambitious titans to forge pacts with their feeble minded mortal slaves. This allowed them to spread their tentacled grasp much farther inland in the ages long past.

Landmass or God? Like lobsters, krakens never stop growing; due to this fact, surfaced eldritch krakens are often mistaken for islands. One of its methods for influencing the surface world is by invading the dreams of the despairing and the isolated. Should the humanoid accept the calling this gives the eldritch kraken an avenue of invasion and the start of its own cult

Wrath of Legend The only time an eldritch kraken surfaces is to execute the final stages of its plan, most often this entails destroying a symbol of the gods it so loathes. When it gets to that place it uses its Krakens Wrath action.

An Elritch Krakens lair

An eldritch kraken's lair is in the deepest rifts in the ocean often to the elemental plane of water.

Lair Actions

On initiative count 20 (losing initiative ties), the kraken takes a lair action to cause one of the following magical effects:

A strong current moves through the eldritch kraken's lair. Each creature within 120 feet of the kraken must succeed on a DC 27 Strength saving throw or be pushed up to 120 feet away from the kraken. On a success, the creature is pushed 20 feet away from the kraken.

Creatures in the water within 120 feet of the kraken have vulnerability to lightning damage until initiative count 20 on the next round.

The water in the kraken's lair becomes electrically charged. All creatures within 240 feet of the kraken must succeed on a DC 27 Constitution saving throw, taking 17 (3d10) lightning damage on a failed save, or half as much damage on a successful one.

Regional Effects

The region around a eldritch kraken is warped by the creature's blasphemous presence, creating the following magical effects:

The kraken can alter the weather at will in an 8 mile radius centered on it. The effect is identical to the control weather spell.

Water elementals coalesce within 8 miles of it. These elementals can't leave the water, have maximum hitpoints and and have Intelligence and Charisma scores of 1 (-5).

Aquatic creatures within 8 miles of it that have an Intelligence score of 2 or lower are dominated by the kraken and aggressive toward intruders in the area. Additionally the eldritch kraken can see and hear through these creatures.

When the eldritch kraken dies, all of these regional effects fade immediately.

Warlocks The eldritch kraken can have a number of warlocks up to its CHA modifier (7) these are the kraken priests in Volo's Guide.