To get this achievement you must make a cumulative total of 20 Uruks run from Morgai Fly nests. The easiest way to gain this achievement is to shoot the nest near the camp which can be seen from the forge tower on the black road.
1. Fast travel to forge tower in The Black Road region.
2. Stand on the NORTH WEST point of the tower and face NORTH.
3. In ability mode (
), you will see an Uruk camp. Under the ruin nearby is a nest. Shoot it down with your bow. The below screenshot shows this nest.
4. Fast travel back to the same tower so that the nest, camp and your arrows respawn.
Repeat as needed until the achievement is yours!