Open either door. They both lead to death. When you open a door and walk through it, a cut scene will start. After the cut scene the final battle with Raam begins.
Take cover behind the rock in front of you. Shoot ram with the Torque Bow. If you can do the active reload, Raam will take less shots. When you run out of ammo for the bow, if you do that is, switch back to the Lancer.
If Raam gets to where you’re taking cover get up and run to the other end of the car. Then take cover there and start shooting Raam again. When Raam is dead the final game cut scene will begin.