The Behilit from Berserk

Well, in that case, I'm curious to hear what your theory is so far. I can elaborate from there. (Because even as far as I am, there are still several unanswered questions.)

Yes, the creator of the Behelit was actually revealed, although the chapter was removed because the author didn't want it to be revealed yet. And it is indeed a being more powerful than the former humans who ascended to godhand status. There are actually multiple behelits floating around. It is unknown whether they are alive or not. Puck, (A pixie who travels with Guts after the golden age ark) comments that the one that he carries around loves to eat cheese, though it's unclear as to whether it really does or not. According to the witch he meets later on, they are "A key that links a deep layer of the astral world to the physical world." And that much is common knowledge to any who aspire to master magic. It is a fetish used for summoning the "Five Angels" (Whom you already could guess.) She goes into deeper discussion about behelits, stating; http://i25.photobucket.com/albums/c59/Rubberpenguin/0202-011.jpg Lesser apostles have been seen with them in their possession, suggesting that not just the godhand have come in contact with them. And later on, we have even seen an artificial one created by the Kushins.