John Glasby & Rand Le Page 
Time and Space [EPUB ebook] 

There were many reasons why the Time Kings sent their warrior hordes back through the endless corridors of Time. The ancient spaceships had been destroyed by the wrath of a people smarting under the aftermath of the Galactic War. But though the lanes of space were deserted to them, the Time Kings possessed a weapon more deadly than any other — the Amphichron. Sweeping through the grey ages, the warriors destroyed and pillaged the peaceful eras of the past.