The Gods--All of them! (Religion)
Hope this helps some. However, bear in mind that the man and the legend are two different things. The fact that he is listed as a bard here does hint at perhaps some time spent in Druidic training, as that was one of the titles many of them took. -The legend of Merlin though, is absolutely steeped in Gnostic meaning, as are nearly all of the surviving ancient myths.