Mastakos is Orlanth's charioteer and, by extrapolation, the god of travel and motion.
Mastakos appeared in Orlanth's service shortly after the Lightbringers returned from their quest. He was not originally part of the quest, but was captured by Orlanth and persuaded into service (a common Orlanthi prize). Now, Mastakos continually travels all over the world, but whenever he is called by Orlanth he is instantly there to serve him.
He is little worshipped; most people prefer to obtain his powers indirectly by worshipping his master.