Assassin Rogue

Feature Description
Bonus Proficiencies At 3rd level, you gain proficiency with the disguise kit and the poisoner's kit.
Assassinate Starting at 3rd level, you have advantage on attack rolls against any creature that hasn't taken a turn in combat yet. Additionally, any hit you score against a surprised creature is a critical hit.
Infiltration Expertise At 9th level, you can create false identities with seven days of effort and 25 gp. If you adopt the identity as a disguise, other creatures believe you to be that person until given an obvious reason not to.
Impostor At 13th level, you can mimic another person’s speech, writing, and behavior after studying them for three hours. You have advantage on Charisma (Deception) checks to maintain your ruse if a wary creature suspects something.
Death Strike At 17th level, when you hit a surprised creature, it must make a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failure, your attack damage is doubled.