User blog comment:KnocknickKnock/9 gates + master of the celestial realm/@comment-2.83.198.8-20131212210042/@comment-7418318-20131213094320

Those are nice theories, but apart from the rarer keys needing more power, they are just that: Theories.

So please don't state it as if it was proofen fact.

Also we were only taking about they keys' material, not about the power of the associated spirit.

And calling the silver keys "tools"? Do you want to guess what Lucy would have to say about it?