Assassin's specialise in infiltration and in dealing precise deadly blows.

Talented Poisioner

When you Select this Archetype at 3rd level if you where not allready proficient with Poisoner's supplies you become proficient with them.

Infiltrator

Starting at 3rd level you may add your proficiency bonus to Dexterity (stealth) checks, and whilst hidden you may also add your proficiency bonus to both active and passive perception checks. At 13th level this bonus increases to double your proficiency bonus.

Assassin's Strike

Starting at 9th level, provided you are not wearing armour whenever you deal damage that could benefit from the Sneak Attack class feature you may treat any random damage rolls for which the rolled result is less than half the maximum possible roll for that die type as if they where half the maximum value instead. At 17th level you do not need to roll and instead treat all damage rolls as the maximum possible value.

Poison Use Expertise

At 13th level you have become so proficient with poisons that poisons applied to weapons you are proficient with weapons will not dry for an hour if it is a melee weapon, and poisons applied to ranged weapons will last indefinitely until the ammunition is used. Provided you apply the poison to the weapon/s your allies may benefit from this provided you apply the poison to their weapon and you are proficient with it.

In addition your knowledge of where to place attacks and exploit physiology means the save DC of any poisons applied to your weapons is increased by an amount equal to half your rogue level. Only you may benefit from this part of the class feature.

Masterful Infiltrator

When you reach 17th level you have become so adept at hiding  that you can do so almost anywhere and with a seemingly unnatural ability. Provided your are considered hidden and are not wearing armour you may render yourself invisible as a bonus action. You may end the effect at any time as a bonus action and it automatically ends if you cast a spell or attack. You may hide in this fashion for a total number of minutes equal to three times your rouge level. This amount may be used all at once or split over multiple uses separated by periods where you are not rendering yourself invisible or even hidden, if you so wish. Once you have exhausted your available number of minutes you must finish a long rest to replenish them.