The Eidolon is the fourth book in The Order of the Sentinels tetralogy, The Eidolon Series. Sentinel Ruben had returned to Mokiem with Sentinel Joe and Sentinel George, where he had momentarily perished for several decades (which is oddly the correct way to describe what happened) at the Battle of Kassam Pass. This book begins as the Sentinels, the Wizards, and the other signatories of the Disseverance make their last stand against the Sorceress and The Collective, who are surging out of the Wastelands of the West in their final push to eradicate the Mokaijem.

This novel encompasses a wide variety of genres, to include Sci-fi/Fantasy, time-travel, action adventures on multiple worlds (primarily on Earth and Mokiem), and is replete with magic, mystery, and romance. For most ages: teens and adults.