The final step for getting an exotic sword is running a Light 300 version of the Darkblade strike on the Dreadnaught. This version adds the elemental-shielded Warden knights from the Founts area to the boss fight, and requires that you kill the Knight with the elemental shield corresponding to the element of the sword you're trying for no more than 30 seconds before killing the boss. Stuntmutt got his on the first try, but Narc didn't, probably because he was dead when the boss died or because he killed his knight too early. Several runs later (after realizing a failure means restarting the whole strike, not just a checkpoint) stabbim comes in to pinch hit for Stunt and Narc gets his sword.