Tros is a spiky, armored ball of an enemy seen in Skyworld's Fortress in Kid Icarus. They adopt a swarming tactic. Pit must be careful and quick in order to minimize the damage inflicted by these monsters. The manual describes them pretty accurately; unless Pit is sufficiently high-powered, these guardians will be a major threat.
In Greek mythology, Tros was the father of Ganymede who grieved for his son after he was taken by Zeus up to Olympus. In return, Zeus granted him two horses that could run over water. Hermes had even comforted Tros, telling him that his son was now serving a much higher honor.