In Camelot, on PX1-767, Merlin's name is rarely mentioned in public. Many believe he was a wizard of darkness, and although he may have tried to do good, there was always potential for great mischief in his heart. Merlin had been neither seen nor heard of since Arthur's departure long ago, and the library where he practiced his strange arts remained sealed, protected by a powerful curse. It is said that all those who enter Merlin's sanctuary forfeit their lives to its guardian, the Black Knight. The door of Merlin's library is magicked, protected by a bluish force field. Ignoring the warnings, SG-1 persuaded Antonius, the village historian, to grant them entry with the key that was kept in the village archive. In doing so, however, they unleashed the Black Knight, a holographic image that appeared and killed Antonius in his home. Despite the danger, Daniel returned to the library, hoping to disable the holographic knight and to find Merlin's weapon.
The library was a large room, filled with ancient books and scrolls and covered in dust and cobwebs. One of the books contained a reference to Merlin's prophetic abilities, similar to the myth on Earth that Merlin could see the future because he actually aged backwards in time, which might have been related to time travel technology. A secret passage behind a bookshelf led to a hidden chamber, in the middle of which stood a platform with an Ancient control console. When Daniel attempted to input a code by pressing specific panels on the device, a treasure magically materialized and filled the room, much as it had done in Glastonbury, and a holographic image of Merlin appeared which repeated the message, "Greetings, friend. I am Merlin. The prize you seek, like the pendulum's swing, marks the passage of all that is before you." However, the activation of the control panel also caused the Black Knight to reappear in the village, and as Mitchell battled the knight with a sword, Daniel tried and failed to deactivate the hologram from the control console until at last he fired his handgun at the device's control crystals, shattering them, and the images of the knight and of Merlin vanished.
The search of Merlin's library did not turn up Merlin's weapon that SG-1 had hoped to find, however Daniel noticed that the hologram of Merlin and all the images of Merlin in the texts from the library depicted him wearing a pendant, something that no material on Earth had referenced. From Meurik, he learned that the blood-red stone of Merlin's pendant is the Sangreal, the device SG-1 sought and the Holy Grail for which Arthur and his knights had quested to Castiana, Sahal, and Vagon Brei.
Episode Reference: Camelot