Perfect World Entertainment is the US subsidiary of Perfect World Co., Ltd., a China-based online game company specializing in MMORPGs. They publish free-to-play, online games and provide online services in North America. The Company primarily publishes three-dimensional, or 3D, online games based on the Perfect World proprietary Angelica 3D game engine and game development platform.
In 2009, Perfect World Co. Ltd. entered into an exclusive agreement to publish Torchlight, an action-MMORPG in production by U.S. game developer Runic Games, worldwide.
Source: Wikipedia, "Perfect World (company)," available under the CC-BY-SA License.