Essence Thief

Essence thieves are rogues make it their goal to understand the true essence of creatures from beyond the Material Plane.  In understanding them, they find ways to augment their movements to match elements of those planes, as well as even temporarily steal the essence of creatures to enhance themselves.  Those few dedicated to this practice can gain abilities to strike with the stolen essence and even move in fantastic ways.

Stolen Essence

Starting at 3rd level, before dealing Sneak Attack damage to a creature, you may force a creature to make a Constitution saving throw contested by your Wisdom modifier + proficiency bonus.  On a failed save, you may remove a single damage resistance of the following types from it (your choice) and gain it yourself until the end of your next turn: acid, cold, fire, lightning, or thunder.  You can use this feature a number of times equal to your Wisdom modifier (minimum of once), and you regain all expended uses of it when you finish a short rest.

At 9th level, you gain the following additional damage types to choose from when using this ability: force, necrotic, psychic, and radiant.

Elemental Mobility

When you choose this archetype at 3rd level, you have learned from studying the elements that you can apply them to help maneuver around in and out of combat.  You gain the following benefits:

Element	Movement Ability
Fire	Fire bursts from under your steps to propel you forward.  Your first turn in combat, your speed is increases by 10 ft.
Earth	You leave no footprints on unworked stone or dirt.
Air	You enable the wind to push beneath your feet, tripling your jump distance.  You may use this ability a number of times equal to your Wisdom modifier per day (minimum of once).
Water	Your feet swiftly glide across water.  You can run across the surface of water as long as you take the Dash action on your turn.

Planar Expertise

At 9th level, your experience and knowledge of the other planes of existence gives you a special insight their very nature.  When attempting to make an Intelligence (Arcana) or Wisdom (Survival) check on an extraplanar creature or environment, you may treat a roll of 9 or lower on the d20 as a 10.

Essence Utilized

Starting at 13th level, you learn to imbue the stolen essence in your attack.  You may end the resistance granted to you through your Stolen Essence feature early and change your next Sneak Attack damage bonus to the resistance type.

Outer Mobility

Starting at 17th level, you have learned to master the movements of the outer planes and have adapted them into yourself.  As a bonus action, you grant yourself one of the bonus movement abilities from the outer planes listed below.  You may use each of these abilities once per long rest.

Outer Plane	Bonus Movement Ability
Upper/Lower Planes	You gain a flying speed of 60 ft. for 1 minute, leaving behind a trail of light or shadow in your wake (if you so choose).  The trail extends up to 30 feet and is 5 feet wide.  This trail is bright light or darkness and lasts until the start of your next turn.
Astral	You warp in space.  You may teleport up to your movement speed to an unoccupied space you can see for 1 minute.
Ethereal	You can move through other creatures and objects as if they were difficult terrain for 1 minute. You take 5 (1d10) force damage if you ends your turn inside an object.