DnD, D&D influenced The Riftwar Saga

Raymond E. Feist's Midkemia began as a homebrew role-playing campaign world, created by a group of friends at the University of California, San Diego, in the wake of Dungeons & Dragons. Feist built Magician on that world. The official Raymond E. Feist site quotes Feist explaining that around 1975, he joined a game being played by friends in an apartment near UCSD. He says Midkemia began as a collection of dungeons and gradually developed into a connected world with cities, geography, and increasingly elaborate world-building.