Planeshifter

Planeshifters are Rogues who have unlocked the power to enter the space between planes to aid in their infiltration, combat, and maneuverability. As such, they are highly sought after by large organizations and wealthy individuals. Usually as assassins and thieves.

Extraplanar Knowledge

Starting at 3rd level, you gain Proficiency in the Arcana skill if you don't already have it. You have advantage on any Intelligence (Arcana) check concerning the planes of existence or a resident of a plane other than the Prime Material plane.

Additionally, you can always see 30 ft into the Ethereal plane, in addition to your normal vision.

Planeshift

Starting at 3rd level, you may begin your journey into the ethereal plane. As part of your action, you shift into the ethereal plane. When you make attacks, you temporarily shift out and in of the ethereal plane. While you move in the ethereal plane, you cannot be targeted by opportunity attacks from other planes and you are able to move through walls less than 5 ft thick. At the end of your turn, you exit the ethereal plane. Doing so takes a toll on your body, you may use this ability a number of times equal to 1 plus your Intelligence modifier, to a minimum of 1. Your uses of this ability reset on a long rest.

Ethereal Jaunt

Starting at 9th level, you begin to understand how to manipulate the barrier between the Planes more proficiently. As a reaction to being hit by an attack, you can roll a d20 and, on a roll of 10 or higher, you are able to force yourself through the border between the Ethereal and Material Planes, dodging the attack and appearing as if you had simply vanished and reappeared. With each successful use of Ethereal Jaunt, the DC is increased by 2 as phasing between realities takes its toll on your body. The DC resets after a long rest. 

Planar Shunt

At 13th level, you have learned how to handle enemies without killing them. When you hit with an attack roll that would deal Sneak Attack damage, you can choose to send the target into the Ethereal Plane instead. The target makes an Intelligence Saving throw, where the DC is equal to half the damage the attack would have dealt, rounded up. On a failure, the target is sent into Ethereal Plane for up to 10 minutes. You can choose to bring them back earlier before the effect ends. On a success, the creature is not sent to the Ethereal Plane, but does take force damage equal to half the amount of damage the attack would have dealt, rounded up. 

Master of Planes

At 17th level, you gain mastery of your Planeshifting. It now gains unlimited uses, and you may shift a number of creatures within 5 ft. of you of your choice equal to your intelligence modifier whenever you use this feature.