I believe this mysterious gods knight is actually the original Vander Decken. Vander Decken was the captain of the flying dutchman hundreds of years ago. But then, according to legend, one dark and stormy night, Decken suddenly "went mad" and began throwing his own crew mates off the ship, resulting in their death. Was this the work of Imu coming down and using a domi reversi on him? Just like Rocks began attacking his own family, wife and kid. Vander Decken then invoked the "wrath of the gods" by cursing him, and as punishment, both he and his ship were cursed to wander the seas forever. (He was granted immortality - turned into a gods knight)