*Must be done on Normal or higher difficulty*
"This is done on "ONI: Sword Base". After you have fought the onslaught of enemies that attack you. You will go around a bend and be put into a sort of bunker with opening doors. On the left you will see the Target Locator. Once the doors open, you will see a rock in front of you. At the bottom of the hill, you will see two wraiths appear and be near each other. Call in the strike in the center of both of them, and destroy them both at the same time. This may take some
timing and aiming/calling in the strike before they come to the area."
Thanks to Sidedish120 over at x360a for the description.