Your eroded and primal mind has difficulty processing things.

 If you fail an intelligence roll, you can choose to reroll it with a strength check instead.

The prolonged exposure to the polluted rain of the Dark Sea has resulted in various mutations. Choose 3 out of these 7 to have.

Chitin: Multiple shells and scales have sprouted all across your body, giving you enhanced defense. Add +3 to your AC 

Bioluminescent Rod: A long, lanky rod with a glowing yellow/teal bulb has grown from your head, giving you the ability to shed bright light in a 30ft radius.

Echolocation: Advanced sensory organs that have grown inside your mouth and brain allows you to making a clicking sound that relays information back to you, useful for navigation and hunting, giving you Blindsight up to 60ft on land and 600 underwater.

Mimicry: Millions of tiny cells that cover your skin allow you to change the color of your body, allowing you to blend in with your environment. Once per short rest, you can activate a mimicry of your background, giving you a +5 to your next stealth roll. Your mimicry deactivates after 5 minutes, at will, or taking any form of damage.

Electric Organ: A powerful specialized defensive organ has grown inside you, letting you discharge high voltages of electricity. Once per short rest, as a reaction, if a creature hits you with an unarmed strike, or a melee attack with a metallic weapon, you can discharge electricity to deal 1d8 lightning damage, and the creature must succeed a DC 10 saving throw or become paralyzed until the start of its next turn.

Ink Cloud: Glands that have developed along the sides of your throat lets you exhale a dense, pitch-black cloud of ink. Once per short rest, as an action, you can expel a 20ft cone of a thick ink in front of you, heavily obscuring the affected area for one turn, and two turns underwater. Any creatures that can see and are inside the cone when the action is used are blinded for 3 turns. You may immediately take the hide or disengage action as a bonus action. 

Siren Song: Your larynx has been mutated to allow you to release a deep alien song. Once per long or short rest, you can emit a low frequency song. Every humanoid within 300ft of you that can hear the song must succeed on a DC 11 Wisdom saving throw or be charmed until the song ends. You must take a bonus action on your subsequent turns to continue singing. You can stop singing at any time. The song ends if you are incapacitated.

Years of living in the abyss of the dark sea has changed your optical receptors, allowing you to see in the dark. You have Darkvision up to 35ft.

Your body has developed gills, letting you breathe not only air, but water as well.

Your intimidating aura makes people shudder in fear from your mere presence. You gain an advantage on intimidation checks, but a disadvantage on persuasion checks due to your less than appealing appearance.

Due to the long exposure to the harsh environment of the midnight zone of the Dark Sea, your body has adapted, but degrading your intelligence in turn. +2 Constitution, - 3 Intelligence.

The cold, unforgiving depths have tempered your body, allowing it to stay warm even in the deepest depths. You have a resistance to cold damage.