Cryptum

The Forerunner Saga is a trilogy of military science fiction novels by Greg Bear, based on the Halo series of video games. The books in the series are Halo: Cryptum (2011), Primordium (2012), and Silentium (2013). The books were released in hardcover, e-book, paperback, and audiobook. Bear was given little restriction on the story of the novel; the Halo universe had not yet been explored in that time period.