Plague stalker

While many rogues are known to master the art of stealth, typically its purpose is to help them avoid battle altogether; whether for ensuring their safety or accomplishing a particular goal. For those who are most acquainted with the underworld, however, the ability to stay hidden is simply another part of one’s arsenal. Said to inhabit the darker corners of urban areas, the ones colloquially known as Plague Stalkers are mercenaries with exceptional skill in pursuing targets from a distance; able to shoot with deadly accuracy while remaining veiled in shadow. They are also masters at crafting and applying different poisons and alchemical mixtures, employing cunning strategies to spread havoc and confusion across the battlefield. Always leaving a trail of caustic agony in their wake, these elusive killers instill dread in the hearts of enemies and allies alike.

Venom expert

When you choose this archetype at 3rd level, you gain proficiency with the Poisoner’s Kit and Alchemist’s Supplies. If you are already proficient with both of these toolsets, you may gain expertise with one of them instead (does not stack with similar features). 

Noxious Bolt

At 3rd level, you embrace the deadly allure of toxicants, fully integrating them into your combat style. You are granted the following benefits: You have proficiency with heavy crossbows. You have advantage on ranged weapon attack rolls made against poisoned creatures. Whenever you hit a creature with a ranged weapon attack for the first time on your turn, they must succeed on a Constitution saving throw (DC 8 + your Dexterity modifier + your proficiency bonus) or become poisoned for a number of rounds equal to half your proficiency bonus (rounded up). Whenever you make a ranged weapon attack with ammunition coated in poison, that poison deals an additional 1d4 damage on a failed save. This damage increases to 1d6 at 9th level, and 1d8 at 15th level.

Deadly Crafts

At 9th level, your ingenuity grants your arsenal a new height of lethality. You learn the Repeating Shot infusion from the Artificer class. You can imbue it into any ranged weapon you are proficient with, even if it is a magical weapon; but may only have a single weapon infused at a time. In addition, any poison you create can be contained in a special venom cask, which may be employed as a makeshift grenade. As an action on your turn, you can hurl the cask at a point of your choice within 20 feet of you. It explodes upon impact with any solid structure or surface, releasing the crafted poison in a toxic cloud. Each creature in a 15-foot cube centered on that point is subjected to the poison contained in the cask (save still required).

Furtive assault

At 13th level, your talent for sneaking around begins to border on the supernatural, as if shrouding your body in a tangible cloak of invisibility. Whenever you succeed on a Dexterity (Stealth) check, you can choose to be treated as invisible for up to 1 minute. This also applies to anything you are wearing or carrying. If you target a creature with a ranged attack while in this state, the target and any others who would be able to see or hear you must make a Wisdom saving throw (DC 8 + your Dexterity modifier + your proficiency bonus). On a failed save, you remain unseen and unheard by them for the rest of your turn. Additionally, as long as you remain hidden, missing a ranged attack in this state does not reveal your position. You can use this feature a total of two times, regaining expended uses when you finish a long rest.

Spray and Pray

At 17th level, you unleash the full might of your weapon, shooting blistering bolts that pierce all creatures caught within their path. Whenever you make a ranged weapon attack, your shot creates a 5 feet wide, 60 feet long line extending from behind the target. All other creatures in the area must make a Dexterity saving throw (DC 8 + your Dexterity modifier + your proficiency bonus), taking your weapon’s damage roll on a failed save. This damage applies the effects granted by the Noxious Bolt feature. In addition, you can now attack twice instead of once when you take the Attack action on your turn, so long as you are currently hidden from the targeted creature/s.