Void Knight

Void Knights are those who utilize their knowledge of the extraplanar to harness the powers of other planes in order to enhance their martial prowess.

Level 3 - Flash Step

You harness your knowledge of the extraplanar to attain unmatched mobility. As a bonus action, you can teleport to an unoccupied space that you can see within 60 ft of you and make a weapon attack from the point you teleport to. 

You can use this feature a number of times equal to your proficiency bonus, regaining all expended uses on a short rest. 

Level 7 - Steeled Soul

You have anchored yourself to your plane of existence. You can not leave the plane of existence you currently reside in against your will, and whenever you would need to make a saving throw in order to teleport using Flash Step, you automatically succeed. 

Level 7 - Extraplanar Combatant

You have attuned yourself to fighting with your extraplanar power. When you make a weapon attack with Flash Step, the attack targets all creatures between the point where you teleport from, and where you teleport to. 

Additionally, when you take the attack action or make an opportunity attack, you can replace one of the attacks with a use of Flash Step.   

Level 10 - Void Slash

You have learned to banish creatures from the material plane. When you hit a creature with a weapon attack as part of a Flash Step, you can force them to make a Charisma saving throw (DC= 8+your proficiency bonus+your Strength or Dexterity modifier) or be banished to a harmless demiplane for 1 minute. The creature reappears in the space they were originally in after the 1 minute passes. If the creature passes the saving throw, they instead take 5d8 force damage. 

You can use this feature a number of times per short rest equal to half your proficiency bonus rounded up.  

Level 15 - Duel In The Void

You can use your extraplanar abilities to force a target to fight on your terms. Once per long rest, you can cast the Forcecage spell. You can freely pass through the cage the spell creates, and when any creature trapped in the cage attempts to teleport you are granted an opportunity attack against them.

Your spellcastng ability for this spell is Strength or Dexterity (your choice). 

Level 18 - Shroud Of The Void

You have become totally attuned to your extraplanar abilities. Once per long rest, on your turn you can undertake a transformation (no additional action required). For 1 minute, you have unlimited uses of Flash Step and Void Slash. Once you exit this transformation, you gain 1 point of exhaustion.