Ghostwalker

With the ability to walk though shadows you can either "shadow walk" long distances while out of combat or be able to "shadow walk" out of an enemies shadow and flank them.

Shadow Walk

While in combat can step into a shadow and walk out of another that is with in 30ft of your position.  While out of combat can shadow step up to 500 miles a day.

Ally Shadow Walk

You may choose a friendly target that is within 5 feet of your position and while maintaining touching contact you can Shadow Walk them from one shadow to another shadow that is 30 feet away.

Enemy Entrapment

You may make a grapple check and force an enemy one size larger than you into their own.  While the enemy is in the shadowfell their sanity is test by all the spirits and must make a wisdom saving throw equal 8+wisdom modifier+ proficiency modifier.  If the succeed they break free and return to the material plane on a failure they take 2d10 necrotic damage.  May use once for every 5 Ghostwalker levels per short rest.  

Shadow Port

With lots of practice of your abilities you have learned to better protect your allies from the forces of the shadowfell.  You have learned how to take a couple of friendly targets throw the shadowfell without letting them succumb to the trauma of being in the shadowfell, by forcing the spirits inside away from you.  Though you strain mentally with more then 2 friendly targets you have learned to not let them take damage.

Etherealness

After pretty much mastering the ability to shadow walk you have learned the ability to appear in both the material plane and the shadowfell, though you appear in both realms your physical body is in the shadowfell and unaffected by any attacks in the material plain.