One of the most promising MMORPGs in development these days is NCSoft's Aion, a fantasy-based offering built on CryEngine. It makes heavy use of flight as a gameplay mechanic, allowing aerial combat and easy travel around the visually stunning game world. There are four basic classes — Warrior, Priest, Mage, and Scout — each of which have two subclasses. For example, Warriors can be tank-like Templars, or berserker-like Gladiators, while Mages can turn into a scholarly Sorcerer or command the elements as a Spiritmaster. Early previews of Aion almost universally comment on how polished the game seems — this is partly due to the fact that it has been up and running since November in South Korea. "Being stable, scalable, reliable and fuss-free is far from a given in MMOs, but Aion is all those things, and can already stand alongside the genre's usability kings, EVE Online and World of Warcraft. Its expansive, zone-free open-world environments look terrific and run smoothly on a wide variety of systems. It just works." Since the game is already in a relatively complete state, NCSoft has been running closed beta "events," where a portion of the game is opened for testing. MMOGamer has a write-up from the latest such event. Aion is due out in September.