Travel to the open-air section of the base and destroy the exposed turrets.
- Go on out of the door that has just opened around the corner.
- Just through the door you will encounter 2 Psions, Legionary, and a Phalanx.
- Fight through them and leave the corridor to reach the open portion of Legion's Anchor.
- Turning the corner to the right you will encounter more Psions and another Phalanx.
- Continue along the corridor to reach the orange shield wall.
- Approaching it will trigger more enemies to come after the Guardian.