The journey from the frouzen mountains to the desert is a long, long one. It's not just a little trip or something, it must take months, according to the novels etc.
Kahvi at least had giant birds to get there. How much Go-Backs came along with Zey? It all just doesn't make sense to me. If they just wanted to start another war, they could get one closer to home, with the trolls. Or did Rayek's ravine seperate them from the trolls? In that case, maybe they 'missed' the sensation of having a war. Or was the little palace so important for our evil Zey? If they were that interested in having a great trophy, they could have thought about something else too. Why go travelling for months to slaughter a whole village of elves? I don't like the way the Go-Back tribe has changed over the years, according to that story, even if not whole the tribe participated, and agreed to the war.