Chrono-Lord Epoch is sent by the the leader of the Infinite Dragonflight to make sure he mixes the past events in Old Stratholme. Some speculate he may be the leader of the Infinite Dragonflight due to other Infinite Dragons and items being named after him, such as Epoch Hunter or 
[Epoch-Mender], but this is false as they all are named after Epochs. On the other hand, other Infinite Dragonflight members have the title "Chrono-Lord" and seem more like lieutenants and less like leaders.
In World of Warcraft, he is located within Culling of Stratholme; an instance introduced in Wrath of the Lich King. According to the achievements, he'll be a boss, killable by players.