This is by means not the only contradiction but it sticks out to me like a sore thumb:
"He seeks Myrdred, an avatara of the Wolf Age whom Balor renamed "The Deceiver" after bending him to his will."
Myth 3 makes it clear for their purposes that the Wolf Age only starts after Mjarin's defeat. However, Myrdred was exiled from the order of the Avatara at the same time, meaning he only classifies as an Avatar of the Wind Age. Also, the Myth 3 epilogue states that Connacht renamed him The Deceiver after his part in Leitrim's death is revealed.
This single sentence from Through the Ermine, if read, could have changed that rather major plot detail and as a result, a different answer would have been given.
This is pretty much why I regard Myth 3 as nothing more than 3rd party material. Damn good music though. As a game, I can't really say much more than the fact that I didn't enjoy playing the solo campaign as much as the previous Myths - far too sluggish and clunky. As for multiplayer.... hah!