Birth place unknown, whether he really existed or not also unknown.
Only, he became a rumor among the people, the one who knows him as a swordsman with an excellent mastership of kendou and was his rival, in this world there is only one I am afraid.
The one who killed the man known as Sasaki Koujiro, the enemy who did not remain in formal history.
希代の剣豪の好敵手として=As a rival with incredible mastership in kendou
祭り上げられた=To set up as someone with an high social status or position (passive)
希代の剣豪の好敵手として祭り上げられた剣士=The warrior who was set up as a rival with an incredible mastership in kendou
希代の剣豪の好敵手として祭り上げられた剣士を=The warrior who was set up as a rival with an incredible mastership in kendou (who is receiveing the action of being 知る)
者=Man (In this case I believe he is doing the action of knowing)
希代の剣豪の好敵手として祭り上げられた剣士を知る者=The man who knows the warrior who was set up as a rival (his rival) with an incredible mastership in kendou
など=And such (It makes this the topic for the rest of the sentence)
Do I understand this sentence correctly?