So I'm drawing off notes I took last night. Kurlos's Fomorian bloodline is what's important. After he is shown the ancient wisdom behind Shadow Court, he understands that his Fomorian lineage is older and more powerful than anything his demon father's bloodline could've given him. Because the Fomorians came from the mysterious black depths of the sea, they themselves are creatures of chaos. Beaten by the Children of Danaan (the Elves), they originate from primordial beginnings, with the emphasis on 'before order'. Shadow Court are chaotic people of darkness. And the darkness of The Endless Winter is what they are most comfortable with. Thus their connection to the Winter Arts.

Kurlos and Daggermouth comprise two of the twelve members of Shadow Court. But what of the others? Will have to give that a think.

So Kurlos is ultimately using his father, Asmodeus. By taking possession of Faerie, Kurlos can give it back to Hell in exchange for Hell's alliance in getting Avalon/Fomora back from the Elves. And in doing so, drive the Elves to extinction.

And so, because Tisandra's lineage is the key to opening Avalon (half Fomorian, half-elf), he needs to track Tisandra to Avalon first before he can reclaim it.

But why would the Fomorians give up Fomoria to fight the Tuatha De Danaan and forsake their hidden land? Because Manannan mac Lir has turned them out, because of his love of a Danaan woman (the beginnings of the Elven kingship) and the betrayal he suffers at Fomorian hands. His wife slain, Manannan curses the land so that only the dead of kings may live within Fomoria. Manannan becomes lord of the underworld. Lord of the Land Under the Waves.

Cast out, the Fomorians have no world left. Their only choice: To battle the Tuatha de Danaan at Magh Tuiredh in the hopes they will occupy the land as their own.

What a beautifully sad way to go. So, once defeated, they have no choice but to incorporate themselves into Elven world. With Avalon closed only to the dead.