In the level Road to Farthen Dur instead of having Murtagh follow you around the whole time you can leave him behind. Once you get Murtagh to one of the draw bridges stay there and kill all the urgals on both sides of the canyon. leave Murtagh behind. After that go ahead and destroy all the ballistae, ruins, and archer towers. Eat the mountain goats and urgals if you get low in health. I'd also suggest when destroyin the archer towers that instead of using all your fire arrows (since they don't always hit your targets) use rocks or exlosive barrels. Believe me I learned this works the hard way after ssoooo many other tries.