Expansions

Perfect World International was first released as an Open Beta on 9/2/2008 (see this thread). Since the game was not reset once the Open Beta ended, this is considered the official release date of the game. Since then there have been a couple of major expansions to the game, which are listed below.

Lost Empires

Released: 12/2/2008
Links: patch notes / expansion page

Added level 79 and 100 skills for each of the original six classes (archer, barbarian, blademaster, cleric, venomancer, and wizard).
Added the Chrono Quests and past maps.
Added world bosses and card bosses.
Added Warsoul weapons.
Added legendary venomancer pets (Baby Blazing Phoenix and Baby Hercules).

Age of Spirits

File:PWI Age of Spirits logo.png

Released: 5/13/2009
Links: patch notes

Added genies. (Many changes were later made to genies in the 9/15/2009 patch.)
Added auto-pathing to quest locations and the "Find Quest" option in the Quests window to find new quests.

Rising Tide

Released: 12/16/2009
Links: patch notes

Added Tideborn lands (three new zones) and assassin and psychic classes.
Added the Raging Tide PvE server.
Added the Palace of Nirvana.
Added a gear upgrade system for high level gear.
Added Public Quests.
Added Marriage Quests.
Added Tidal Protection Charm Quests.
Added Account Stash.
Added TAB targeting.
Added custom key settings.

Genesis

File:PWI Genesis logo.png

Released: 3/2/2011
Links: patch notes / expansion page

Added Earthguard lands (four new zones) and mystic and seeker classes.
Added faction bases.
Added faction diplomacy feature.
Added Divine Contract daily quest.
Added Runecrafting skill.
Added a leveling guide that pops up when you hit a new level (unless disabled at level 21 or higher).
Major user interface update.