The Forerunner Saga is a 2-book series with 2 released primary works first released in 2011 with contributions by Greg Bear.
The Forerunner Saga is a trilogy of Halo novels focusing on Forerunner life 100,000 years before the Human-Covenant War, written by Greg Bear and published by Tor Books. The series reveals a great deal of new information about the Forerunner-human interactions in ancient history, as well as providing additional background for the events in Halo 4 and subsequent media.