At 1st level, choose two of your skill proficiencies, or one of your skill proficiencies and your proficiency with thieves' tools. Your proficiency bonus is doubled for any ability check you make that uses either of the chosen proficiencies.
At 6th level, you can choose two more of your proficiencies (in skills or with thieves' tools) to gain this benefit.
Beginning at 1st level, you know how to strike subtly and exploit a foe's distraction. Once per turn, you can deal an extra 1d6 damage to one creature you hit with an attack if you have advantage on the attack roll. The attack must use a finesse or a ranged weapon.
You don't need advantage on the attack roll if another enemy of the target is within 5 feet of it, that enemy isn't incapacitated, and you don't have disadvantage on the attack roll.
The amount of the extra damage increases as you gain levels in this class, as shown in the Sneak Attack column of the Rogue table.
During your rogue training you learned thieves' cant, a secret mix of dialect, jargon, and code that allows you to hide messages in seemingly normal conversation. Only another creature that knows thieves' cant understands such messages. It takes four times longer to convey such a message than it does to speak the same idea plainly.
In addition, you understand a set of secret signs and symbols used to convey short, simple messages, such as whether an area is dangerous or the territory of a thieves' guild, whether loot is nearby, or whether the people in an area are easy marks or will provide a safe house for thieves on the run.
Cunning Action
Starting at 2nd level, your quick thinking and agility allow you to move and act quickly. You can take a bonus action on each of your turns in combat. This action can be used only to take the Dash, Disengage, or Hide action.
Many rogues walk a fine line between life and death, risking their own lives and taking the lives of others. While adventuring on that line, some rogues discover a mystical connection to death itself. These rogues take knowledge from the dead and become immersed in negative energy, eventually becoming like ghosts. Thieves' guilds value them as highly effective information gatherers and spies.
Many shadar-kai of the Shadowfell are masters of these macabre techniques, and some are willing to teach this path. In places like Thay in the Forgotten Realms and Karrnath in Eberron, where many necromancers practice their craft, a Phantom can become a wizard's confidant and right hand. In temples of gods of death, the Phantom might work as an agent to track down those who try to cheat death and to recover knowledge that might otherwise be lost to the grave.
How did you discover this grim power? Did you sleep in a graveyard and awaken to your new abilities? Or did you cultivate them in a temple or thieves' guild dedicated to a deity of death?
Echoes of those who have died cling to you. Whenever you finish a short or long rest, you can choose one skill or tool proficiency that you lack and gain it, as a ghostly presence shares its knowledge with you. You lose this proficiency when you use this feature to choose a different proficiency that you lack.
As you nudge someone closer to the grave, you can channel the power of death to harm someone else as well. Immediately after you deal your Sneak Attack damage to a creature on your turn, you can target a second creature that you can see within 30 feet of the first creature. Roll half the number of Sneak Attack dice for your level (round up), and the second creature takes necrotic damage equal to the roll's total, as wails of the dead sound around them for a moment.
You can use this feature a number of times equal to your proficiency bonus, and you regain all expended uses when you finish a long rest.
As a bonus action, you give yourself advantage on your next attack roll on the current turn. You can use this bonus action only if you haven't moved during this turn, and after you use the bonus action, your speed is 0 until the end of the current turn.