Unless stated otherwise, all information herein is taken from TWoRJTWoT, Ch. 18.
Raken are one of the Seanchan exotics, taken from worlds accessed via the Portal Stones to fight Shadowspawn. They are large flying animals, longer than a horse and about as intelligent. They have grey skin and eyes on the front of the head, which is supported by a long neck. They have a range of up to around four hundred miles and are the most highly regarded of all the exotics. Over short distances, they can fly four times as fast as a horse can run, but can fly longer distances at lower speeds. As with some horses, they can be ridden to the point of death. Their main use is carrying messages and scouting, they can have two riders, who ride in a special saddle, though the Seanchan can over-rely on them, and fail to adequately use ground scouts (TGS, Ch. 5)