Raging war between Embron empire and the Horde fueled the inovation on the battlefield. Under the King's command, special troops were created, wielding sniper rifles and imbuing the ammunition with artificer magic. Their goal was elimination of the enemy ranged units, taking them out as quickly as possible.
War ended, but the troops remained, now usually headhunters looking for the horde separatists. As years passed, majority of surviving decimators became bounty hunters, looking for contracts to make a living.

Bonus proficiencies

When you choose this archetype at 3rd level, you gain proficiency with firearms and disguise kit. 

Marksman

At 3rd level you learn how to disable targets more efficiently. While you're prone, you add your intelligence modifier to your spell save DC.

Steady Aim

At 7th level, whenever you are prone and no opponent is within 10 feet of you, you gain advantage on your ranged attacks and your attacks produce no sound nor reveal your location.

Arcane Mark

At 11th level you master firearm wielding.  Whenever you use your Hunter's Mark you can choose one effect which lasts until Hunter's Mark is dissmised:

• Your firearms attacks score a critical hit on a roll of 19 or 20 against marked target.
• Targets have disadvantage on saving throws against your spell saving DC.
• Your ammunition deals Force damage, and your ammo is not consumed.
• You get +2 to attack and damage rolls.

Prepared Combatant

At 15th level, you ignore reload and misfire properties.