After years of research of the Far realm it has learned to pull small pockets of madness from the far realm and effect those who seek to harm you.

Unknown Side Effects

Starting at level 2 you find reaching out to the far realm has an effect on you.You have grown one of the following.

Tendril-This gives you advantage on strength checks and saves. The tendril comes from your shoulder, upper chest, or arm and cannot be moved. (can lift up to 20 pounds)

Eye-This third eye gives you advantage on perception checks to see things.This eye originates on the hand but can be moved at will. (can see 120ft in the dark) 

How ever if either of these are visible you have disadvantage on persuasion checks.

Unprdictable Casting

Starting at 2nd level you embrace the pure madness of the far realm, and (as long as you have the components on your person) you can use any hand motion, words, or components to cast spells. This may confuse those wishing to counter your spells.

Shared Madness

When you successfully affect a creature with a spell you can cause it to make a Wisdom saving throw with your spell save DC. On a failed save the creature takes an additional 3d6 psychic damage. (If this is used on multiple targets the damage is reduced to 2d6)

You can do this a number of times equal to your Intelligence modifier per long rest.

You are also immune to fear.

Far Reach

Starting at 10th level you can plunge your hand into the far realm. As an action you open a small portal next to you placing your hand into it and opening a larger portal next to a creature within 30 ft. as a larger version of your hand comes out it forms into tendrils and grapples the target. These tendrils can grab 1 Giant or Large creature and 2 Medium or smaller creatures. Both the creatures affected and the creatures within 10ft must make a Wisdom saving throw or be frightened. They are frightened until the end of their turn.

The DC to escape the tendrils in your spell save DC

 

Clay Skin

You gain the other effect of "Unknown Side Effects".

Unstable Stability

Starting at 14th level you can attempt to fully reach out to the far realm. At the beginning of a long rest, you can go into a trance state as you make an intelligent save with 20 as the DC. On a success, starting at the end of the long rest your AC and saving throws gains a +5 for the next 12 hours. On a failed save you become paralyzed for the next 8 hours not receiving a long rest. (You can not use this feature again until you are no longer affected by this feature.)

Being affected by the Far Realm can be whatever best fits your game for example. Tendrils around the mouth, Several extra eyes, Dark misty fog around you.