Yorn Nuro is the leader of the pirates located at the nysillin farm in the FeluciaCombat zone. He is weaker then Scratch and C-21 Highsinger. When fighting players, Nuro can "freeze" players, stopping their ability to move.
A good way of defeating him is to jump all the time while attacking him at the same time. He will not be able to target you while you are jumping.