Defeat the big blue guy with chain

Answer from: bonzo
If its the cave troll in Mines of Moria you are on about then you need to switch to hobbit, go through the hatch at left side which takes you up onto a ledge kill the boxes or whatever on the small platform jump up here then jump on the trolls head and hit the appropriate button (x) once its stunned you need to switch to legolas and shoot arrows in its mouth/face. This may take a couple of tries to get. Then you repeat the above at the right hand side hatch