Have you noticed how smart the giants in ROTR are? They are experts in warfare and know more about the Sandwens than the Sandwens know about the giants. And they specifically chose to bring Redfire to the parlay. Why? Because they knew the Sandwens would love to get him. The build of the Desert Herd steed is very unique among pegasi. And in the first/second book when the giants captured the wild herd they knew the Sky Guard would find out and attack. That's why they tied the windings in a VALLEY. Seems easy, but the peaks above are trap holders. And in the first book they hit Fort Prowl with such force that the Sandwe warriors would leave the farms and go fight and other giants would destroy the food supply.
And side not: is Redfire the only Desert Herd steed? In book 3 it was mentioned that he was on a mission only he could accomplish and no one else could ride jet stream. Seems like Desert Herd flunked the journey and only River Herd, Mountain Herd, Jungle Herd, and Snow Herd will live on. Unless Redfire sires a mixed breed. Or if there is a Desert Herd steed but a young one?