I think your explanations, Azmere, all make good sense. A very good point about the ring becoming OP should you remove the limitations. As for the quick sidenote to the ST's you suggested, it seems to me like that should fit. I think there are OOC notes in the actual wiki already (usually placed at the bottom of articles), so adding one here isn't really unusual or anything.
Concerning the selection section (rhyme), what you added makes perfect sense. But I guess I just don't know how a player OOC would know when their character might be able to summon the ring. It's a game logistics thing I'm concerned about.
Though it could be I'm overthinking this and like a lot of things the ring would only be granted to a player by mod decision. Was that what you had planned?
Sorry to keep picking on this point. It's probably really annoying, but I just want to make sure. ^_^'