The invasion was facilitated by an enchantment that Morgause cast on her half-sister Morgana. The spell utilized Morgana herself as an energy source for a powerful enchantment that put every person in Camelot (including Uther Pendragon) to sleep, allowing Morgause and her Knights to enter the castle unchallenged. Morgana herself was unaffected by the enchantment, as were Merlin and Arthur Pendragon, who were outside of the kingdom at the time of the initial enchantment.After returning, Arthur and Merlin found Morgana, and the three rushed to protect Uther from Morgause and her Knights, moving him to a servant's quarters while being pursued by the Knights. Arthur repeated fought off the Knights as he and Merlin began to feel the effects of the sleeping spell. Merlin secretly searched Gaius's grimoire for a counterspell to wake the King, but was unable to find out, and he subsequently sought the counsel of the Great Dragon, who revealed that Morgana was the source of the enchantment, and that she had to be killed to lift the spell. Merlin then returned to Gaius's chambers and retrieved a bottle of hemlock, which he emptied into a water bag. He then gave the water to Morgana, who drank it, and began to feel the effects of the poison immediately. Morgause abandoned the fighting and rushed to Morgana's aid, but Merlin refused to tell the sorceress what poison he used until Morgause ended the invasion.