Level 3
Dead of Night.
While you are hidden, when you hit a creature with a firearm attack, another ally that is adjacent to the target can make an opportunity attack against it.
Natural Camouflage.
If you have not moved during your turn, you have advantage on stealth checks.
Level 7
Run and Hide.
Reaction: When you hit by a melee attack, you can move up to half your speed. If you end your movement adjacent to another ally, you can attempt a stealth check to hide.
Level 11
Sleep With One Eye Open.
You gain advantage on stealth checks. When you succeed on a stealth check, you can move up to half your speed (replaces Natural Camouflage).
Level 15
Silent as a Ghost.
(1/round) When you critically strike with a ranged attack while hidden, you don't become revealed.