I don't think there's any piece of equipment that comes as a helmet, shield, and ring. I don't know what that part of the clue meant otherwise, but it must not be that so I'll ignore that part of the clue.

I'll guess thornlet, "crown of kings" being a reference to Jesus and the crown of thorns. If that's it, you'll have to explain to us the part about "shields and rings."

Also, if I'm right someone can take mine because I don't have the energy to think of something obscure in the game and make up a rhyme about it.