Aion is a fantasy game set in Atreia that combines Player versus Player, or PvP, and Player versus Enemy, or PvE. It features a class system to designate player roles, crafting custom items, a quest system, and combat using skills that the player avatar learns. Temporary avatar flight is also possible in restricted zones. It has one expansion pack, titled "AION: Assault on Balaurea" and released in 2010.