Ya you can't do no knight strat on challenge mode, those ogres have to go down without moving, really only 1 can stray off, 2 if you want a real struggle. I'd say watch YouTube and see how it's done bro. It's actually super easy it's just sometimes you are in a group that won't click and get it done, usually 1 person scrubbing it up for everyone and not able to notice it....