Death Gate is an adventure game loosely based on Margaret Weis and Tracy Hickman's fantasy book series The Death Gate Cycle.
The player takes the role of Haplo and starts in the Nexus with Lord Xar. Lord Xar tasks Haplo to visit the four worlds, Arianus, Pryan, Abarrach and Chelestra and retrieve the seal pieces of these worlds. Xar plans to undo the Sundering with the Reformation, the act of recreating the Earth again and he needs the seal pieces to do so.
Source: Wikipedia, "Death Gate", available under the CC-BY-SA License.