Meridian 59: Evolution is a free-to-play, open source, 3D PvP-oriented MMORPG. Its original incarnation was released in 1996 and is widely credited as the first graphical MMORPG. That original release was overhauled and relaunched in 2002, with 3-D graphics and many new upgrades.
The game does not have a class system, but rather a skill system based on one school of weaponcraft and six schools of magic based on the game's patron gods of Shal'ille, Qor, Kraanan, Faren, Riija, and Jala. The usual questing, monster hunts, and raising skill levels, exploration, and character customization are there. PvP is the bread and butter of Meridian, and most of the recent updates have focused on adding new modes and tweaking the system.