Lovecraftian Abomination

As the follower of a god from the far realms, your physical form can become twisted and grotesque in any number of ways. Usually this manifests as spider legs growing from you, your limbs turning into tentacles,  or eyes growing randomly across your skin. As a bonus action you can have one of these effects manifest for up to 1 hour. While active, you must maintain concentration as if focusing on a spell. Using these forms places a strain on frail mortal bodies, and can cause people to abhor you. While this feat is active you have disadvantage on all Charisma skill checks besides Intimidation. After you end the transformation you have disadvantage on all strength, constitution, and dexterity saving throws for an amount of time equal to your transformation.  You can use this ability up to a number of times equal to 1 plus your constitution modifier until you complete a long rest.

Legs of Atlach-Nacha

Four long spider legs burst out from your abdomen, two on each side. Any clothes you are wearing in that area will tear at the point they erupt from. While they are active you gain the following benefits

• You gain a climbing speed equal to your walking speed
• You have advantage on saves against being knocked prone, being pushed, or pulled.

Eyes of Cthulu

Yellow eyes with  black slits for pupils manifest over your skin in random locations. While they are active you gain the following benefits.

• You gain advantage on Perception and Investigation checks relying on sight
• You can see Invisible creatures within 15 feet of you

Corruption of Azathoth 

Your form becomes obscured as you shift into a mass of writhing tendrils. While in this form you gain the following benefits,

• You have advantage on Dexterity Acrobatics checks against being grappled
• You cannot be restrained by non-magical means
• You can fit into spaces half your size

Form of the Fish-Men

You grow gills, and fins form along your arms and legs. While in this form you gain the following benefits,

• You gain the ability to breathe both air and water
• You gain a swim speed equal to your walking speed
• Melee attacks underwater do not impose disadvantage