The Domino ability costs 4 runes to unlock and is exclusive to Emily Kaldwin.
Mission 6: Dust DistrictNear the beginning of the mission, you'll come to a fork in the road. To your left is the Crone's Hand Saloon and to your right is the Overseer Outpost. Head towards the Overseer Outpost until an Overseer blocks your path. While facing the Overseer, look for some rocky ledges to your right. Climb up and Far Reach to a balcony above you. This balcony wraps around and puts you right in front of the Overseer Outpost. Look for an execution taking place in front of the Outpost and use Domino on the shooter and one of the captives. When they both fall, the achievement will unlock.