Once a month guardians defend an outpost from the vex, fallen, cabal and hive. They all attack from different sides of the square complex and guardians must defend them from getting in. Sniper position would be up high and good coverage down low would allow a small number of guardians to guard each side. The outpost could even be down on earth as long as there is flat ground and adequate space to fight. What would be good is if you could override doors and close them until the enemy break through allowing you time to get ready if they breach the walls.