Unlike the regular Darknut and Darknut Lv. 2, Lv. 3 is not obtained from any of Echoes of Wisdom 's dungeons. Instead, you'll have to brave the depths of a cave in eastern Faron Wetlands.

You can also use the Grappling Hook against an unarmored Darknut for a chance to steal its Knight's Crest. Some chests, particularly in dungeons, contain a Knight's Crest.