The Mask

This is the Mask subclass from the Seas of Vodari unofficial book.

Double Life

Costumed Disguise. Your costume can be of any design that hides or disguises your face. This disguise should include changes to your voice and demeanor. Your costume has no impact on your worn equipment or Armor Class. You can create an additional costume (or replace a lost costume) over the course of one day of work(8 hours) by expending 25gp worth of materials. You can maintain up to two costumed disguises at a time. 

Signature Weapon. You can designate a finesse or ranged weapon as your signature weapon, such as a rapier, whip, dart, or longbow. While using your signature weapon, you gain a +1 bonus to attack and damage rolls. This weapon is as important a part of your masked persona as your costume. Your signature weapon should have a name, sound, identifying mark, or be used with a certain flourish, that links it to your masked persona. You can change your signature weapon to another finesse or ranged weapon during a long rest by expending 5gp worth of materials in addition to the purchase cost of the weapon.

Secret identity. You can switch between your masked persona and your normal persona in one minute. If a creature with an intelligence of 6 or higher sees you switch between identities, they learn your secret identity. Otherwise, the ability to connect these personas using observation is impossible, unless you choose to share the fact that you lead a double life.

Better In a Crowd.

Starting at 3rd level, you are used to facing multiple enemies at once and can use their numbers against them. You gain an additional way to use your Sneak Attack: you don't need advantage on the attack roll to use your Sneak Attack against a creature if you are within 5 feet of two or more hostile creatures, as long as you don't have disadvantage on the attack roll. All the other rules for Sneak Attack still apply to you.

Sidekick

At 9th level, your work as a Mask has developed a network of allies that you can draw on for knowledge and support during your downtime. Your most important ally is your Sidekick. You and your GM can decide the relationship and backstory for you and your Sidekick. Your Sidekick is a race and gender of your choice, gaining all racial traits and using the stats of a "Sidekick". Your sidekick is inexperienced and in training, so accompanying you on adventures is usually too dangerous. Your Sidekick focuses on conducting surveillance and scouting out locations ahead of time for you. If you and your sidekick team up and spend four hours carousing within a populated area, you gain the following (at your GMs discretion):

Knowledge of guard patrol routes, rotations, and key locations in the area such as jails, fortresses, and armories.

Knowledge of locations of heavy criminal activity and hideouts of local crime groups.

Knowledge of popular locations used by nobles and politicians for secret meetings.

Access to a temporary safe house that is hidden from your enemies. You can continue to access this safe house for 1 week before a new safe house will be need to be established.

Strike Fear

Starting at 13th level, your reputation is well known and strikes fear in the hearts of your enemies. While operating as your masked persona, you have advantage on Charisma (Intimidation) checks against creatures that are familiar with your secret identity. 

In addition, your signature weapon attacks have become terrifyingly effective. If you hit a creature with a sneak attack using your signature weapon, the target must make a Wisdom saving throw with a DC of 8 + your proficiency bonus + your Charisma modifier. On a failure, the creature is frightened of you until the end of your next turn.

Archenemy

Beginning at 17th level, you have gained the ability to determine the capabilities of your enemies using repartee and analysis. You can use the bonus action granted by your Cunning Action to dsignate a creature within 30 feet that can hear and understand you as your Archenemy for 1 minute. When you do so, your attack rolls against the target have advantage until the start of your next turn. 

In addition, your weapon attacks score a critical hit on a roll of 19 or 20 while the creature is designated your Archenemy.

Also, if you hit a creature designated as your Archenemy with an attack, you can make a Wisdom (Insight) check contested by the creature's Charisma (Deception). If you succeed, you learn one aspect of the creature of your choice: Armor Class, Creature type, Current hit points, Lowest or highest saving throw ability

Once you have used this feature, you can't use it again until you finish a short or long rest.