Ugh I seem to be stuck. :/ I have gone everywhere I can with the helmet key and have one stone and metal emblem and one metal emblem ( I don't remember needing to find a stone ring to go around the emblem all those years ago). Every room on my map is green and I just can't think of what I am missing. I might be taking a little break while trying to come up with an answer.
Side note: It feels like I have over 15 hours already on this playthrough going so slow lmao
Edit: Thanks msdstc I might reveal that spoiler if I can't come up with anything, but I really want to come up with the answer on my own if I can. I just needed a bit of a vent as I spent an hour re-exploring places I knew did not contain the answer.
I think what you need to do is use the
crank on the outdoor pool to fill it up again, so you can go behind the waterfall.
I was stuck for a while here too.