You focus your training on the grim art of death. Those who adhere to this archetype are diverse: hired killers, spies, bounty hunters, and even specially anointed priests trained to exterminate the enemies of their deity. Stealth, poison, and disguise help you eliminate your foes with deadly efficiency. 

Assassinate

Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. You have advantage on attack rolls against any creature that hasn't taken a turn in the combat yet. In addition, any hit you score against a creature that hasn't taken a turn in combat yet is a critical hit. 

Wetwork

When you choose this archetype at 3rd level, you gain the ability to Disengage as a reaction.

Additionally, you gain Wetwork dice, each of which are a d6, and are representative of your honed skills in the art of stealth and assassination. You have a number of these equal to twice your proficiency bonus, each of which can be used to buffer your abilities or execute maneuvers as listed below.

Like a Shadow: When you feel it applicable, you can use one of your Wetwork dice to add to a Dexterity check of any kind, including your initiative rolls. You may also add this bonus to Perception checks if you are successfully hidden. 

Blade in the Dark: If you are successfully hidden and have advantage on an attack, you may expend one of your Wetwork dice to add a bonus to an attack roll on a versatile or thrown weapon.

Swift as the Night: As a bonus action, you can expend one of your Wetwork dice, multiplying the result by 5 and adding the total to either your jump height/distance or movement speed for the round. 

Infiltration Expertise

Starting at 9th level, you can unfailingly create false identities for yourself. You must spend seven days and 25 gp to establish the history, profession, and affiliations for an identity. You can't establish an identity that belongs to someone else. For example, you might acquire appropriate clothing, letters of introduction, and official- looking certification to establish yourself as a member of a trading house from a remote city so you can insinuate yourself into the company of other wealthy merchants.

Thereafter, if you adopt the new identity as a disguise, other creatures believe you to be that person until given an obvious reason not to.

Additionally you gain the ability to expend one of your Wetwork dice to cast Alter Self at will to either assume this identity or another of your choosing. Choosing the identity you have crafted grants you advantage on all Charisma checks as that person. 

Shadowed Nightmare

At 13th level, you gain the move through the shadows like a figment of someone's worst nightmare. You may, as a bonus action, using one of your Wetwork dice, Teleport up to 30ft in shadows or darkness, becoming invisible for one round afterwards, or until you attack a creature and dispel the invisibility.

You may also choose to attempt to frighten your enemy instead as a bonus action, expending a Wetwork die in the process. The DC for the frighten effect is 8+Proficiency+Dexterity. 

Death Strike

Starting at 17th level, you become a master of instant death. When you attack and hit a creature that hasn't had its turn yet, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, double the damage of your attack against the creature. You may also stack your Wetwork dice in the damage roll for this attack.