From the Main Menu, select Firefight
then Private Match
to invite a friend. You can change the Difficulty
but you must leave the Game Options
. When you are both ready, select Start Match
. One of you needs to select a UNSC leader, while the other selects a Banished leader.UNSC Leaders
Launch = Captain Cutter, Isabel, Professor Anders
Add-on = Sergeant Forge, Kinsano, Sergeant Johnson, Commander Jerome, SerinaBanished Leaders
Launch = Atriox, Decimus, Shipmaster Let' Volir
Add-on = Colony, The Arbiter, Yap Yap THE DESTROYER
Awakening = Voridus, Pavium
Protect the Terminus, then at the start of round 5 (wave 21) the achievement will unlock.
The other person doesn't need to play, I just set up two barriers at each entrance and held off the enemies by myself.