I am using DDG's assist function: "Paul Edwin Zimmer write a fourth Dark Border novel".
DuckAssist Result: The fourth novel in Paul Edwin Zimmer's Dark Border series is titled "Ingulf the Mad." This book focuses on characters Ingulf Mac Fingold and Carrol Mac Lir, detailing their meeting and the acquisition of their mystic swords, while the main character from the earlier novels, Istvan Divega, does not appear.
DuckAssist Result: The fourth novel in Paul Edwin Zimmer's Dark Border series is titled "Ingulf the Mad." This book focuses on characters Ingulf Mac Fingold and Carrol Mac Lir, detailing their meeting and the acquisition of their mystic swords, while the main character from the earlier novels, Istvan Divega, does not appear.