On this quest, you have to retrive the blade from the norn that goes nuts and starts killing the other norns. There are two phases. one pre-transformation after you get him low in health he goes to the monster form and resets health.
If you transform him into a moa bird on the first part, he will drop the sword before you defeat him. If you pick it up then defeat him in full, you get stuck as it says ‘pick up the sword’ which you already did. If you don’t transform him all works fine.