Here's o1-preview after thinking for 7 seconds, > As of my knowledge cutoff in October 2023, Paul Edwin Zimmer did not publish a fourth novel in the Dark Borde

Here's o1-preview after thinking for 7 seconds, > As of my knowledge cutoff in October 2023, Paul Edwin Zimmer did not publish a fourth novel in the Dark Border series. The series comprises three books: > 1. The Lost Prince (1982) > 2. King Chondos' Ride (1982) > 3. A Gathering of Heroes (1987) > > Paul Edwin Zimmer had plans to continue the series, but he passed away in 1997 before any additional novels were completed or published. There have been no posthumous releases of a fourth Dark Border novel. If there have been developments after October 2023, I recommend checking recent publications or official announcements for the most up-to-date information.