Robin beat Twilight to the punch with that question. However, as she pondered it herself, she came up with her own answer. "Because our natural powers aren't what's needed."

She turned to the sage and questioned it. "It's the Onion Knight of legend, isn't it? I haven't read too much about it since I got here, but it's a part of it and we need to master it. Also, like I've surmised, they weren't taken, just locked."