Use Legolas to shoot the 3 targets inside the fires. Build the stairs then use Gimli's jump + Square to smash the rock. Use Aragorn and pick up the green item. Follow the green mist using Aragorn to track the surroundings. Once you've followed enough, two small scenes will show up, then you will be able to build a rope device. Switch to Legolas and shoot the target on the left, pick up the rope and attach it to the rope device. Pick up the green item and track the area again using Aragorn until you reveal a breakable floor. Use Gimli to jump-smash the floor, pick up the green item and track again using Aragorn to reveal the path up north.
Follow the path down. Break the rocks, go downhill. Avoid the shots while beating the orcs that come down, wait until they slide down then hit them. Move along, jump up the bars beside the upper ledge on the right, jump with one character first, switch to the other, jump to the other bar. Build the ladder. Climb up the ladder. Hit the orcs. Continue along. Beat some more orcs. Continue to the right. An armored orc will appear, keep attacking to destroy him. Crawl under the small hatch. Move to the right. Smash the trees, build the ladder and climb up.
Use Fangorn to simply trample and walk over the orcs to destroy them. When you reach the barrier, pick up the rocks using Fangorn and throw it at the barrier to destroy it. Move along the path. As Fangorn, pick up Merry and cross over the river. Stomp along some orcs while walking down the path ahead. Switch to Merry and crawl at the hatch, jump to the vines to bring down some water and douse the burning log. Walk ahead.
Follow the studs to reach the next chapter.