Kill 20 enemies while linked to the Mobile Cover Drone.

Mission 4: Fission

After you zipline out of the Warbird at the start of the mission, you will notice these "riot shields on wheels" in front of you. Simply go up to one and press [ Register or Signin to view external links. ] to use it and you will become linked to it. Whenever you aim, the shield will go down. Whenever you aren't aiming, the shield is up. Use the [ Register or Signin to view external links. ] to move and simply kill 20 enemies while using it. There are a lot more than 20 enemies in this initial section, so getting 20 isn't that difficult. For an exact location of the Mobile Cover Drone, see the video below for a visual walkthrough.