Follow the path. Use Aragorn's blade to beat the ghosts and smash all the glowing pillars. Build a ramp once all four pillars are destroyed. Walk up and move along. Once you see a breakable rock on the floor, use Gimli to break it, build the hatch then enter it. Switch to Legolas, jump up on Gimli's ledge, shoot the target, jump over the bar and to the upper ledge. Push down the crate. Build the ladder and climb up using Gimli, jump over the bars and shimmy upwards. Jump over to the platform on the right and jump-smash the rock. Move along. Use Legolas to shoot the targets and build the bridge. Continue ahead. Once you reach another area, go to the upper left and smash the rock using Gimli, build a jumping bar and use Legolas to jump up. Don't approach the smoke since Legolas gets disturbed by the ghosts, just shoot the target, jump across to the right and push off the crate. Jump up to the ledge, hit the red rocks using Aragorn and continue ahead. Use Gimli to destroy the rock on the wall. Move along. In the next area, go to the right and smash a red rock using Aragorn, push off the statue and climb up the ladder. Use Legolas to cross the rope, switch to Aragorn, pick up Gimli and pass him to Legolas. Smash the rock and build a hatch, enter it. Use the turnstile and enter the gate.
Hit the four rocks using Gimli, build the platform and hit the King of the Dead using Aragorn. Once the King is hit, he will exit and summon skulls to flood towards you, go to the sides of the room to avoid this. Build the platforms from the skull debris and hit him again. On the last part, you need to build four platforms. Jump over to the platform where the King is near and slice him with Aragorn. Quickly jump to another platform to avoid his counter-swipe after you hit him. Do this 3 more times.
Follow the path to reach the next chapter.