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. This is a reworked version of the (in my opinion) rather underwhelming assassin subclass, in an attempt to make it more widely usable and fun to play. One of my players is currently playtesting it, so let me know if there is anything that could be improved upon!

Assassinate

Starting at 3rd level, you are at your deadliest when you get the drop on your enemies. Any hit you score against a creature that is surprised, or that hasn't taken a turn in the combat yet, is a critical hit. Additionally, you also add your proficiency bonus to initiative rolls.

Art of the Con

At 9th level, you gain access to one of three different features from the options available to you. You gain another feature at 13th level, and your chosen features get stronger at 17th level. The upgraded versions for each feature are currently listed under the options for Marked For Death.

Over the course of your years in the rogue trades, you have had plenty of experience perfecting the various cons you have employed upon unsuspecting marks. Whether it be to infiltrate a building to find your target, to allay suspicion when you get noticed, or to escape capture after being caught, you have a whole list of tricks you can use to fool anybody and everybody, including those who should've known better.

...and I think he called you stupid too!

As an action, you can force a creature to make a Wisdom saving throw, using your Charisma modifier to determine the DC. On a success, nothing happens and the target becomes immune to this feature for 24 hours. On a failure, the target becomes charmed by you for 24 hours, regarding you with ambivalence, neither hostile nor friendly, but becomes hostile to any creature you choose that it can see. You may choose any number of creatures up to your Charisma modifier. The target may repeat the saving throw any time it takes damage, and the spell ends if you attack the target.

You've heard the term, the enemy of my enemy is my friend. But what if the enemy of my enemy is actually my enemy? And it turns out that my original enemy is actually an undercover guard who has been lying to my enemy this entire time? And all of a sudden a fourth enemy comes in and professes his undying love for the third enemy and turns on all of us. Wait, which enemy is that again? Through subterfuge and confusion, you can get an enemy to turn on their allies by challenging what they know, or what they think they know about their loyalties. Or, if the enemy is dumb enough, just say their friend called them fat and watch the punches fly.

Bavarian Fire Drill

Upon choosing this feature at 9th level, you may choose to gain advantage on any Charisma check used to exercise authority over a person you do not otherwise have authority over, by convincing them you have it. This could be a deception, persuasion, intimidation, or performance check, depending on your DM's discretion.

By utilizing a person's deference to a higher authority, you boldly claim to have authority over a person, have the right to be wherever you are, or have the right to do whatever you're doing at the moment. The Bavarian Fire Drill is a social engineering tactic where you get what you need done by acting as if you already have the authority to do it.

Refuge in Audacity

Upon choosing this feature at 9th level, you may choose to make a Charisma (Performance) check any time you intend to deceive a creature you are not in combat with, contested by the creature's Wisdom (insight) check. On a success, you have advantage on any Charisma (deception) checks you make against this creature, until the creature is given significant reason to doubt the ridiculous story or persona you have adopted.

Your preferred tactics are a little unorthodox compared to other people in your trade, with your plans and actions so over-the-top and dramatic that nobody can ever understand how they work, including sometimes yourself. Your methods are so ridiculous that people who are suspicious of you usually don't bother you, as most people come to the obvious conclusion that nobody could make up such a ridiculous story.

Slip into Shadows

At 13th level, you choose between one of three abilities that showcase your extraordinary talent and skill at stealth and subterfuge. 

Black Gateway

Upon choosing this feature for Slip into Shadows, shadows become mere doorways for you. While in an area of dim light or darkness, you may use a bonus action to teleport instantaneously, passing through the surface of the Shadowfell and reappearing in another area of dim light or darkness that you can see. Teleporting in such a way is silent, and does not give away your position to anybody who couldn't already see you. You may use this feature a number of times equal to your proficiency bonus.

Shadowy Ambush

Upon choosing this feature at 13th level, you gain the ability to use your Sneak Attack feature from a distance. You can use the Attack action on your turn to target a creature you can see within 20 feet of you. You may not target a creature with this feature if they do not fit the requirements of your Sneak Attack feature. Choose an unoccupied space within melee range of your target, if there is no such space, you cannot target the creature in question. You teleport into the shadow of your target, attempting to strike at them from the darkness before reappearing in the space you left. 

Shadowy Embrace

Upon choosing this feature at 13th level, you gain access to the spell Invisibility, and can cast it at will without expending a spell slot. You may cast the spell in such a way a number of times equal to your Dexterity modifier.

Marked for Death

Provided that you know a creature's name, face, and have some amount of information on their daily routine (an amount at your dm's discretion), you can know where they are at any given moment, even predicting deviations from their routine, practically being able to see them through walls. You also have advantage on all charisma-based skill checks against them, and have advantage on all attack rolls against them. You may only have one creature marked for death at one time, and you may choose a new Mark at the end of each long rest.

You used to study your marks day in and day out, to the point where after a few months, you knew every inch of their house, every obscure and slight mannerism they had, even their own history and family, better than even they know them. Now, you have no need for this level of work, you've seen every mark a thousand times. If you know a person's face, name, and a general idea of what they do or where they work, you can read the lines in their face and know just about everything about their history, you can guess just about where they are on a momentary basis, and you have an advantage in any conversation you may have with them.

...and I think he called you stupid too!

As an action, you can force a creature to make a Wisdom saving throw, using your Charisma modifier to determine the DC. On a success, nothing happens and the target becomes immune to this feature for 24 hours. On a failure, the target becomes charmed by you, regarding you and creatures you choose with ambivalence, neither hostile nor friendly, but becomes hostile to any creature you choose that it can see. You may choose any number of creatures to be treated as hostile up to your Charisma modifier and you may choose up to the same amount to be treated neutrally. The target may repeat the saving throw any time it takes damage. 

You've heard the term, the enemy of my enemy is my friend. But what if the enemy of my enemy is actually my enemy? And it turns out that my original enemy is actually an undercover guard who has been lying to my enemy this entire time? And all of a sudden a fourth enemy comes in and professes his undying love for the third enemy and turns on all of us. Wait, which enemy is that again? Through subterfuge and confusion, you can get an enemy to turn on their allies by challenging what they know, or what they think they know about their loyalties. Or, if the enemy is dumb enough, just say their friend called them fat and watch the punches fly.

Bavarian Fire Drill 2.0

Upon reaching 17th level, you automatically succeed on any Charisma check used to exercise authority over a person you do not otherwise have authority over, by convincing them you have it. This could be a deception, persuasion, intimidation, or performance check, depending on your DM's discretion.

By utilizing a person's deference to a higher authority, you boldly claim to have authority over a person, have the right to be wherever you are, or have the right to do whatever you're doing at the moment. The Bavarian Fire Drill is a social engineering tactic where you get what you need done by acting as if you already have the authority to do it.

Refuge In Audacity 2.0

Upon reaching 17th level, you may choose to make a Charisma (Performance) check any time you intend to deceive any creature, even if you are in combat with them, contested by the creature's Wisdom (insight) check. On a success, you have advantage on any Charisma (deception) checks you make against this creature, until the creature is given significant reason to doubt the ridiculous story or persona you have adopted.

Your preferred tactics are a little unorthodox compared to other people in your trade, with your plans and actions so over-the-top and dramatic that nobody can ever understand how they work, including sometimes yourself. Your methods are so ridiculous that people who are suspicious of you usually don't bother you, as most people come to the obvious conclusion that nobody could make up such a ridiculous story.