He is in the library when he stumbles upon the Knights of Camelot. He flips through the pages and a name catches his eye. He asks Ron if Merlin was real. During the History of magic class, Harry asks if Professor Binns could tell the class about Merlin. There is a temple and guardian for each amulet.
Legend says that the guardians are five times bigger then any human.
Now back to the stuff we are supposed to learn. Harry got very interested in this Merlin stuff. He got as many books on Merlin as he could, but there was one in the forbidden section he wanted to look at. He got a permission slip from professor Binns. In the book there was a map that showed the position of the virtue temples.