This is the description of one the tournaments conducted in 宝蔵院 in a videogame:
My initial translation would be:
Houzouin's oldest contest with the aim of allowing practitioners of martial arts from all over the world to hone the basics. The fact that anybody can participate is what is said to be Houzouin's gateway to success.
I'm having lots of trouble properly parsing the second sentence.
First off, how does と言われるゆえん work here? I've googled ゆえん and found that it's an old expression meaning 理由 (seemingly interchangeable), e.g. in following sentence:
The reason that this school is said to be prestigious is due to the many famous people that have graduated from here. (this is my own translation)
But I can't for the life of me piece together what ゆえん in my sentence is actually referring to.
Second, what does 登竜門 here refer to? I understand it means gateway to success but does it refer to 宝蔵院, saying that the reason the school got so successful is due to the fact that anyone can participate or does it refer to the 武芸者, that it can be a gateway to success to anybody who wants to participate?
If somebody could break down the second sentence for me, I'd be very much obliged. Thanks!
Edit: Upon further thought, if I broke the second sentence down into the following:
The fact that anyone can participate is the reason why it (宝蔵院最古の闘技) is called the gateway to success (at Houzouin).
Does that make sense?