Your eldritch heritage gives you a bonus to your constitution and the knowledge imparted to you grants you a bonus to your wisdom or intelligence.

+2 con and +2 wisdom or Intelligence

As part of your birthright as a spawn of Cthulhu, You have a set of tentacles that you can extend by splitting open your character's jaw.
These Can be extended or retracted at will without taking an action. While extended these tentacles grant you a +4 to grapple and can be used to make unarmed attacks dealing 1d6 Psychic damage.

While your tentacles are extended as an action you can use the power of Cthulhu flowing in your veins to cause a cone of maddening fright to wash over those you gaze upon.

The cone extends out 30ft, and all in it must make a DC15 wisdom save or be Frightened it may try another save at the start of its next turn for 2 turns

Acts as the Fear spell.

at 11th this increases to DC18 wisdom save.

This ability can only be used twice a day and replenishes on a long rest.

As a spawn of Cthulhu, you are a creature of the sea as well as land, While in the water you can breathe water, have a swim speed equal to your speed on land, and can sense the creatures around you while submerged out to 60 feet.

Starting at 6th level you may form a pair of Leathery wings as an action granting you a fly speed of 10 ft.

These wings are rather bulky when formed and take up a large amount of space. They require a 10 foot space to allow for flight comfortably.

Due to your eldritch origins, you have advantage on all saves against Frightened.