Ethereal Blade

The Zhentarim and other similar organizations prize the capabilities of martial warriors, illusory casters, Assassins, Thieves, and so many other forms of talent. Many Rogues implement the ability to throw darts or daggers and do so with measured success but fail to do so versus more than one target at a time. Who do the Zhentarim call upon from their ranks when they need someone who can deal with multiple targets discreetly and swiftly? Who do they call upon when conventional Assassins or illusion arcanists won't be able to handle specific missions? Who do they call when they need an audacious distraction that might be able to swiftly end many enemies while grabbing attention?

On the surface, the Ethereal Blade Rogues hone their ability to launch a plethora of weapons in the same amount of time it takes a regular Rogue to land a single blow or an illusionist to prepare and sling a spell. Additionally, they are able to tap into minor amounts of ethereal power to aid them in their endeavors on the material world. Once one digs deeper, they might find that an Ethereal Blade Rogue is able to draw the attention of their enemies - affording their allies the opportunity to strike. This comes at the cost of their usual deft precision with each strike. 

Ethereal Blade masters are even able to magically conjure an insurmountable number of blades from the Ethereal Plane and bury them deep into a vast number of foes. 

Bladestorm

Starting at 3rd level, you can use the bonus action granted by your Cunning Action to make two ranged weapon attacks with thrown weapons so long as both attacks target different creatures. You may only use this feature if you have enough weapons on your person to throw. Once you have no weapons left to throw, you must replenish your supply of thrown weapons.

Upon reaching 13th level in this class, you are able to draw on the essence of the Ethereal plane as a substitute to real weapons. Whenever you use the Bladestorm Cunning Action, you may choose to have the thrown weapons be Ethereal Darts. These function the same as regular darts but deal Force damage instead of piercing damage.

Upon reaching 17th level in this class, your Ethereal Darts count as +2 magical weapons.

Ethereal Authority

Starting at 3rd level, you are able to command a tiny bit of essence from the ethereal plane. As such, you are able to draw on the magical energy energy of the plane to suit your needs in the material world through the manipulation of a spirit to serve you or the creation of invisible messages.

You gain the Find Familiar and Illusory Script spells. You may only cast them as rituals. Your spell casting ability for these spells is Intelligence. When you cast Find Familiar using this spell, you draw a spirit from the Ethereal Plane in order to craft your familiar. Therefore, your familiar will have the Undead creature type. Moreover, you may add Crawling Claw and Homonculus to your list of available familiars. All of your familiars are considered proficient in the Stealth skill if they were not already.

Audacious Distraction

Starting at 9th level, you have the ability to draw the attention of whole crowds of people.

When you use your Bladestorm feature, you may expend your Action to put on a small performance. During the brief performance, you silently draw some energy from the ethereal plane and implant the essences into the minds of the creatures around you. All creatures of your choice within 30 feet of you must make a Wisdom saving throw. The save DC is equal to 8 + your proficiency bonus + your (Strength or Dexterity) modifier. Upon a failure, the creature is drawn in by your impressive display. Until the beginning of your next turn, the effected creature is charmed or frightened of you (your choice). Upon a success, they are unaffected. 

You may use this feature twice and regain the ability to do so when you take a short or long rest.

Ethereal Reciprocation

By 13th level, you have learned enough about the workings of magic that you can improvise the conjuring of an ethereal blade as a reaction to immediate danger.

When you or a creature you can see within 30 feet of you takes damage, you may use your reaction to throw a single Ethereal Dart at the attacker. You make a ranged weapon attack with your improvised Ethereal Dart. Upon a hit, the target takes 5d6 + your Dexterity modifier Force Damage.

Ethereal Salvo

When you reach 17th level, you have become a master of swift bladework. More than that, you have become proficient at conjuring blades form the ethereal plane in order to react to your enemies. Now, you have learned to combine the two crafts into a single, devastating volley of ethereal judgement.

As an action, you throw a single weapon with the thrown property of any kind. When you do, you swiftly move your hands as if throwing dozens of weapons. Dozens of copies of the original thrown weapon launch from yourself to create a cone of identical Ethereal weapons that shoot forward and then disappear. Each creature of your choice in a 60-foot cone (with you as the source) must succeed on a Dexterity saving throw. A creature takes 6d6 Force damage on a failed save, or half as much damage on a successful one. 

Once you use this feature, you can't use it again until you finish a long rest.