"Keep the magic secret"

Keep the magic secret is the tagline for Series 1 of the show Merlin. It is used for publicity and is designed to reflect a key aspect of the show's protagonist, Merlin.
 * "It's lonely to be more powerful than any man you know and have to live like a shadow. To be special and have to pretend you're a fool. I know how it feels, I understand."
 * —Merlin to Gilli


 * "I just want Arthur to trust me and to see me for who I really am."
 * —Merlin to Gaius

"You can't let Arthur know about your gift.''"
 * "''If it comes to a choice between me saving peoples lives and revealing who I really am, there is no choice."
 * —Merlin and Hunith


 * "How many times, Merlin?! How many times must I drive it into that thick skull of yours that your magic is a secret to be guarded with your life?! What were you thinking??!!"
 * —Gaius to Merlin


 * "Father, please! I can't allow this! This is madness! There's no way Merlin is a sorcerer. ... Merlin is a wonder, but the wonder is that he's such an idiot. There's no way he's a sorcerer."
 * —Arthur


 * "Arthur thinks he is so sharp! But even when I told him I was a wizard, he still couldn't see it."
 * "Sometimes they're pretty hard to spot."
 * "Well, maybe I should go around wearing a pointy hat."
 * —Merlin and Gaius

The tagline is based on the fact that Merlin has magic but in Camelot such powers are forbidden, which is made painfully clear in The Dragon's Call (Series 1, Episode 1) when a suspected sorcerer is executed as Merlin first arrives in Camelot. On pain of death, Merlin must keep his gifts a secret. The only people in the show who know about his powers are Hunith, Merlin's mother, William, Merlin's childhood friend, Gaius, Kilgharrah, Nimueh, Mordred and the Druids, Edwin Muirden, a warlock who was killed after attempting to get revenge on Uther for the deaths of his parents, Lancelot, a deceased knight of the round table, Freya, Merlin's deceased love-interest who was cursed to be a Bastet and returns as the Lady of the Lake, Taliesin, an ancient warlock and seer, Gilli, a young and misguided warlock who left Camelot after Merlin opened his eyes to how magic should be used, stating that their paths may cross again, The Cailleach, Julius Borden, a student of Gaius who is thought to have died while pursuing a dragon's egg, Agravaine, Arthur's uncle who is also deceased, Alator of the Catha, a warrior and High Priest of the Old Religion, who swore his allegiance to Merlin, and many of the minor foes Merlin has defeated. Of these, Gaius, Kilgharrah, Lancelot, Freya, and Nimueh have played a major role in the plot of the show as a whole. Mordred will be returning in Series 5 and will serve as a main character. Gaius, Kilgharrah, and Lancelot were the only main characters to know Merlin's secret and to be his long-time allies. Gaius is Merlin's mentor and main confidant. At one point, during The Witchfinder (Series 2), Gaius submits himself to being sentenced as a sorcerer in order to protect Merlin's secret when Aredian planted evidence implicating Merlin as a sorcerer. Merlin then proved Gaius's innocence. In The Mark of Nimueh (Series 1), Merlin confessed to sorcery.