Concealment

Stalker Technique: 7th, 9th, 13th, and 17th level You've become adept at evading creatures that rely on darkvision. While in darkness, you are invisible to any creature that relies on darkvision to see you in that darkness. Additionally, when you hit a creature with a ranged weapon attack while hidden, you can force that creature to make a Dexterity saving throw against your tech save DC. On a failed save, the creature's speed is reduced to 0 until the end of your next turn. You can use this feature three times. You gain an additional use at 9th, 13th, and 17th level. You regain all expended uses when you finish a short or long rest.

Granted by Stalker Technique at 17th level.