Prince of Persia: The Forgotten Sands

This is story related and cannot be missed.

After you have obtained the previous trophy (A Warm Welcome) you will be told to open the big gates for Malik. As necessary cross the beams and press the 3 switches, once this is done watch another cut-scene. After that has finished you need to make your way down to your brother, cross the beams and make the necessary jumps to get there. You will land in a big room full of treasure where Malik will greet you, watch the cut-scene where you see the sand army being released, after this is when you will get the trophy.