Sniper

As a Sniper, you pick and choose your targets and opportunities from afar. Why get up close and messy? Your weapon of choice is the light crossbow and your skillset revolves around using it well and getting it into advantageous position for maximum damage to your target.

You likely learned your skills hunting as a child, or in the army as part of a corps of arbalists. But yours is a specialty. It takes nerve and the ability to shut out the world around you. No different than waiting for the deer in the forests back home. Patience is rewarded with opportunity. That is the lesson.

You've learned how to best hide yourself and keep a low as possible profile, even inside with little cover. You've learned anatomy to better identify your target's weaknesses. You know how to use your eyes to see and your ears to hear. You've learned stealth, accuracy, and planning, along with the rogue's skills you absorbed on the side. 

How you use your skills is up to you, but you're well-set to be an asset to any group of adventurers. When they start to see the bodies falling, there won't be any doubt.

Sniper Archetype

At 3rd level, when you select the Sniper archetype, you gain a number of proficiencies, skills, and feats. Dexterity (Stealth), Wisdom (Insight), Wisdom (Perception), and Intelligence (Nature) are job requirements. As is the Crossbow Expert feat. 

These things are essential to being an effective Sniper.

Sniped Shot

When you accept this archetype at 3rd level, you gain the ability to make a sniped shot from advantage if you are undetected by your target, surprise them, or they are within 5 feet of a creature attacking them. Use the rogue's sneak attack rules as your guide. If successful, this attack is treated as a critical hit doing double damage + your DEX mod + your proficiency bonus. If your roll to hit is a natural 20, the damage is treated as a double critical, doing four times weapon damage and twice your DEX modifier and proficiency bonus. 

At levels 9 and 15, add another d8 piercing damage to your damage total.

Additionally, at levels 9 and 15, your chance for a critical hit Increases. At 9th level it's on a natural roll of 19 or 20. At 15th level, it's on a natural roll of 18, 19, or 20.

Dexterity Bonuses

Starting at 9th level, you have so effectively learned to blend into your environment that you have expertise with the Dexterity (Stealth) skill. 

You gain a +2 bonus to your initiative rolls and Dexterity saving throws. Any Dexterity ability checks are rolled with advantage. 

Your accuracy has improved with your Dexterity and you gain a +2 bonus on your ranged attacks. 

Your movement speed is increased by 10 feet and you receive a +2 bonus to your AC score.

Bespoke Scope

Starting at 9th level, you've enlisted the help of a master artificer with a talent for grinding glass. She has made you the most amazing gadget to mount on your crossbow. It's a magical telescope designed to help you make better aimed shots, with crosshairs etched onto the glass. She really is a master craftsman. I fear she may be too expensive for me the next time I'm in need of her services. 

This scope grants a +2 bonus to hit on your ranged attacks and on damage. 

Extra Shot

At 9th level, if you miss a shot, you can use a bonus action to rapidly reload and take another shot at a -5 penalty to hit. You can use this feature three times per long rest. 

Instakill

Starting at 13th level, your sniped shots can instantly kill a target on a critical roll unless the target can make a CON saving throw. If they fail their throw they are reduced to 0 hit points immediately. If they make their roll, they suffer their normal damage.

Improved Scope

Starting at 17th level, you've acquired an improved version of your old scope. Not only does it add an additional +2 bonus to your shots, it expands your critical hit range to a natural roll of 16-20.