Homebrew Cthuul Species Details

Ability Score Increase. Your Constitution score increases by 2, and another ability score of your choice increases by 1.
Age. Cthuul share similar life expectancies to common men.
Alignment. Cthuul's alignments vary from group to group, but tend to skew towards evil and chaos.
Size. Cthuul are Medium creatures.
Speed. Your base walking speed is 30 feet.
Darkvision. You can see in dim light within 60 feet of you as if it were bright light, and in darkness as if it were dim light. You can't discern color in darkness, only shades of gray.

Animal Enhancements. Your body has been altered with animal characteristics. You choose one animal enhancement now and one at 5th level.
Nimble Climber (1st level). You have a climb speed equal to your walk speed.
Underwater Adaptation (1st level). You can breathe air and water, and you gain a swim speed equal to your walking speed.
Grappling Appendages (5th level). You have two special appendages growing alongside with your arms. Choose whether they're both claws or tentacles. As an action, you can use one of them to grapple a creature. Each one is also a natural weapon, which you can use to make an unarmed strike with. If you hit, they do 1D6 + your Strength modifier bludgeon damage. Immediately after hitting, you can try to grapple the target as a bonus action. These appendages are not dexterous enough to use weapons, magic weapons, and other specialized equipment.
Carapace (5th level). Your skin in places is covered by a thick shell. You gain a +1 to your AC when not wearing heavy armour.

Cthuul Traits

The Cthuul are a monstrous race of men, deformed by their dealings with the strange beasts of the sea.

Nimble Climber OR Underwater Adaptation

Nimble Climber (1st level). You have a climb speed equal to your walk speed.
Underwater Adaptation (1st level). You can breathe air and water, and you gain a swim speed equal to your walking speed.