A couple of incosistensies:
1) the Callieach weren't destroyed in the Valley of the Red Seal, the Oghers were (you said that both met they're ends there).
2) we do not _know_ that there is a spider "world," Whether the fetch come from there, whether the Smiths were Dwarves, or whether the Tain leads o the "Spider World." These are theories of yours and hence, while they may be true, are not in Myth's "real" history
-Discordia
BTW: It's not that innately disagree with any theories put up here, it's simply that the only way to test them is to prove them wrong. Devil's Advocate an' all ;)
