Whether a hired professional, or seeking to resolve a personal matter, assassins are masters at tracking and killing their mark. Make use of the opportunities that you create, or commit to a direct attack, regardless of your method your mission is clear, your mark must die.

Bonus Proficiencies

When you choose this archetype at 3rd level, you gain proficiency with the disguise kit and the poisoner's kit. If you are already proficient, you may double your proficiency bonus when making checks with these tools.

Situation Assessment

Beginning when you select this subclass at 3rd level, you've honed your situational awareness allowing you to take advantage of the initial confusion of a fight. You gain a bonus to initiative equal to your intelligence modifier (minimum of 1), and have advantage on attacks against creatures that have not acted yet in combat.

Mark

When you take this subclass at 3rd level, you commit yourself to eliminating very specific people and creatures called your marks. As a bonus action on your turn, you may designate a creature you can see as your mark, you may also spend 10 minutes to designate a creature that you have identifying information for, such as their name or image. While a creature is your mark, you have advantage on Intelligence (History, Investigation) and Wisdom (Insight, Perception) checks relating to them, and deal additional damage to them equal to your intelligence modifier.

You can only have a number of marks equal to your proficiency bonus at a time, and may only designate a number of creatures up to your proficiency bonus per long rest. A creature remains marked until it dies or you end the mark as a bonus action.

Seize Opportunity

At 9th level, your instincts and reflexes have been sharpened to avoid wasting an opportunity that presents itself. Your weapon attacks against your mark score a critical hit on a roll of 18, 19 or 20.

Master Infiltrator

Starting at 13th level, you can unfailingly create false identities for yourself. Vou 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 unerringly mimic another person's speech, writing, and behavior. You must spend at least three hours, or one hour each, studying these three components of the person's behavior, listening to speech, examining handwriting, and observing mannerisms, or one hour each. Your ruse is indiscernible to the casual observer. If a wary creature suspects something is amiss, you have advantage on any Charisma (Deception) check you make to avoid detection.

Follow up Strike

Starting at 17th level, you can strike with deadly speed. If you take the Attack action on your turn, you can make one additional attack that targets your mark. This attack can benefit from your Sneak Attack even if you have already used it this turn, but you can't use your Sneak Attack against the same target more than once in a turn.