Saint Seiya: The Lost Canvas or simply Knights of the Zodiac is a spin-off manga series Saint Seiya, released in 2006 and ended in April 2011, in chapter 223 (The future that begins), in Japan. The manga tells the stories and the battles between the Knights of Athena and the Evil Stars of Hades at the time when the legendary Dohko of Libra and Shion of Aries were 18 years old, ie in 1743.
The events narrated at the beginning of The Lost Canvas are the same as those at the beginning of the Next Dimension manga, although there are some differences between the narratives. The manga has the full approval of series creator Masami Kurumada, who is working on the Next Dimension manga. Lost Canvas is a prequel and takes place before the original series.
The two manga tell in part (beginning of "Next Dimension") the same story, but with differences in the names and stories of some characters. Canvas chronicles an alternate version of Next Dimension's Holy War. Saint Seiya: Next Dimension - Meiou Shinwa is the official sequel/prequel to Saint Seiya, made by the original author of Saint Seiya.
Our favorite gold knight in this saga is Cancer's Manigold, after all, he and his master (also a cancer knight, but from a generation ago) managed to imprison the God of Death Thanatos. Quite a grand achievement.