Halo

Chakas and Riser--two humans who live a hundred millennia before Master Chief--find themselves on one of the Forerunner's ancient Halo rings. In an effort to get off the ring and back to Erde-Tyrrene--Earth--to find out why the Librarian would tamper with human destiny. In so doing, they meet the Captive, the last of the Precursors--those who came even before the Forerunners, who spread the seeds of life across the galaxy--and he has a vendetta against all sentient life.