Wisps

Two guards stand either side to a gate, silently watching the crowds meander by. When a thin fog envelopes them both, but not enough to completely cover their vision. In the minor confusion one looks at the other, and sees him slumped over. A thief in grey standing over his body. The remaining guard swings at her form, as it strikes her body it swirls into a wisp of smoke, as she plunges her dagger into him from behind. 

Bonus Proficiencies

When you take this archetype at 3rd level, you gain proficiency in the Deception skill if you don’t already have it, and you gain proficiency in the disguise kit

Smoke and Mirrors

Striking your opponents weakest point allows you enough time to slink back into the haze, poised to strike again. At 3rd level, When you do successfully deal damage using your sneak attack feature, a 10 by 10 ft cube of smoke appears in your space. This smoke is lightly obscuring and winds of moderate speed or higher (at least 10 miles per hour) can disperse it. You can use the hide action to attempt to hide in this smoke. This smoke lasts until the end of your next turn.

Vapor step

You become one with the fog, allowing quick movement to avoid danger whenever possible. At 9th level when you use your Uncanny Dodge feature while in light or heavy obscurity created by fog, smoke, etc. you can choose to teleport up to your movement away and become invisible until the end of your next turn or you attack or cast a spell.

Now You See Me, Now You Don’t

Your smoke acts as a beacon for the attention of your foes, so you use it to distract them until you can strike from behind. At 13th level, you can use your bonus action to create the same cloud of smoke you create with the Smoke and Mirrors feature, except it lasts for 1 minute and follows you as you move. You can use your bonus action on subsequent turns while the smoke cloud persists to teleport your movement away from your current position and become invisible until the end of your next turn or you attack or cast a spell, doing so however has your cloud stop following you, instead remaining where it was when you teleported. You can use this feature a number of times equal to your Dexterity modifier per short or long rest.

Hazy Falsehood

Your smokey deception manifests as illusions you shape and manipulate to assist in your deadly assault. At 17th level you can use a bonus action to create an illusionary clone of yourself. The clone shares your initiative and goes immediately after you. It shares all your racial abilities, class abilities, feats, equipment, languages, and stats with the exception that it cannot have more than one hit point at any time. Creatures that cannot see through illusion have to make a contested Wisdom (Insight) check vs your Charisma (Deception) check to discern if it is an illusion. Your clone cannot activate magic items or magical effects (for instance if you have a +1 Flame Tongue sword your clone gets the +1 but cannot activate the flame). You can use your bonus action when summoning your clone and on subsequent turns to command it mentally. If you do not command it, it will take the attack action against the nearest hostile creature on its turn. The clone lasts for 1 minute or until it drops to 0 in which case it vanishes in a puff of smoke. You may summon an amount of clones equal to your proficiency bonus per long rest.