He was approached by the alien Time - Keepers -- time travelers from the end of the universe preserving timelines rather than conquering them in exchange for immortality .
Time travelers from the end of the universe are the last living creatures in existence -- to become their agent .
He was approached by the alien Time - Keepers -- time travelers from the end of the universe , the last living creatures in existence -- to become their agent , preserving timelines rather than conquering them in exchange for immortality .