User blog comment:GWAINE/Merlin - Episode 5.10 - Press Release/@comment-4892425-20121116003122

If Morgana is now worried about Emyrs, it could only be one thing: in 5 x 09, Merlin, as Emyrs, dropped the ACME anvil on Morgana, thus freeing Gwen from the enchantment and thwarting her plans to take Camelot once again. As she grumbles "curses, foiled again!" Morgana remembers Alator did find out from Gaius who Emyrs was, and Alator refused to tell her. As far as she's concerned Alator is a traitor and Emyrs is a roadblock to Camelot and a threat to her life. Sounds like Merlin/Emyrs takes out a big chunk of her hide and Morgana will lose a bit of her swagger. She bullies those she perceives as weak (i.e., people that are not magical and cannot fight back on the same level), but she is scared witless when it comes to Emyrs. She has to get to him before he gets to her.