Ok, I've got too little free time lately (got a job as a Mac tech/salesman/etc), so I'll make my comments on everything brief:
The cycle is a thousand years of light and a thousand years of Dark, and a new Leveller and a new Hero appear at the start of each one. The point at which the destined victor makes his big appearance (Connacht attacking the Krids, Balor destroying Muirthemne, etc) is the start of the the Era.
Old Greek/Helenistic/Roman generals were gay and there was nothing wrong with this. I'm of Roman descent and I take no insult; I think they were way more open-minded than the modern homophobes.
MB the Hed givs gud hed mb? (KIDDING! jeez, calm down!)
The Smiths of Muirthemne built the walls of Muirthemne, hence the spiders.
Fetch are from the Spider world; the Tain is an intermediary world between the two worlds.
And finally: because I said so, that's why.
