Climb onto the low wall outside of Helm's Deep using a rope, then head up the stairs to the right and destroy the Silver gate there to get the brick inside. On the southern end of the inside of Helm's Deep, use a Strong Character to pull the orange handle and then push the block underneath the Small Character Hatch. As in previous multi-objective brick challenges, go around and hit the statues twice so it only takes one hit to destroy them, then switch to Legolas and shoot an arrow at each to quickly win the Mithril brick. Look for the hoping statues and destroy all 7 within 8 seconds of one another. Walk up the ramp into Helm's Deep and climb up onto the wall from the rope hook.
Jump down to the right from the main ramp into Helm's Deep and destroy the Morgul object to grab a Mithril brick.