User blog comment:20thCentFopp/The Power of Legend: Thor vs. Merlin/@comment-4652104-20131019144640/@comment-4652104-20131020175010

Well, I gave it more thought and it occurred to me that King Arthur (and Merlin by extension) is probably not a pre-Christian Anglo-Saxon figure. In the medieval romances he is a chivalric age character (early Christian Norman or Anglo-Saxon). If there is any historical origin for Arthur, it is a Celtic figure, probably from the late Roman period. They would therefore not be followers of the Norse gods, although they may be familiar with them as enemy deities.

In Marvel, Arthur is placed in the 6th century, which would make him either a late Celt or early Anglo-Saxon. So it could put him on both sides of the divide. Although I'm not sure this would have been established at the time of this comic.

However, all this speculation is unimportant, since the Merlin in this story is this guy: http://marvel.wikia.com/Maha_Yogi_(Earth-616)