The "Hour 20" news team has requested a special match. Fight Reaper enemies alone in the Armax Arsenal Arena.
After completing two matches, check the Combat Sim Controls in the Armax Combat Arena to read the following e-mail:
You will need to use one of your prizes from a previous match to purchase Reaper enemies for the combat simulator. It is a silver level prize. After doing so, simply set the simulator to Reaper enemies and no squadmates, and complete the combat to finish the mission. Since most arena challenges are not mutually exclusive to each other, the other options can be set in a way to finish other arena challenges at the same time, e.g. Citadel Arena: Medi-Gel Challenge or Citadel Arena: Thermal Clip Challenge.
After the match, check the control terminal to read an e-mail congratulating Shepard.