I guess that what I got from both endings of Myth 3 (depending on who won the final battle) is that the winners write the histories, and seldom accurately.
Now, the history says that Miarin's head was never seen again, and no one could recall its fate. I have very little doubt that Connacht took care to hide the head in the deepest part of Muirthemne, and that nothing had ever been seen of the head during Connacht's reign. Perhaps, just as Connacht knew that he would become Balor, so might he have known that Miarin's head would be vital to Balor's downfall... but he would have a good reason to withhold both pieces on information even from his best friends, let alone his subjects.
Another thing that sort of bugged me: In Myth 2, it says about Myrdred that "Balor renamed (him) The Deceiver, after subverting him to his will." Whereas Connacht's shrine said that Connacht had named him The Deceiver long before he had so much as become Balor, let alone subverted the Fallen Lords to his will.
Maybe I take Myth 3 too seriously, and should assume that none of it happened. After all, the winners write the histories. Still, something to think about, I guess.
