Wikipedia
AdventureQuest (also referred to by its website name BattleOn or abbreviated to AQ) is an online flash-based single-player role-playing video game started in 2002 and currently developed by Artix Entertainment. As of February 6, 2015, aq.battleon.com, the game's hosting website, and www.battleon.com, the game's homepage, have an Alexa rating of 31,549.
A one-time "guardianship" fee was introduced in 2003, allowing the player to access more in-game content. Ownership of the game transferred to the newly formed Artix Entertainment in 2004, and a server population cap was added for non-Guardian players in May of that year. In 2005, a microtransaction system was put into place. In response to criticism that server restrictions made logging on for non-paying players difficult, in October 2006 Artix Entertainment introduced a server in which a player could log on at any time, but with a tight level limit. As of July 14, 2010, the server cap has been removed entirely.