Brand Materia

I visited the Glimmer Man, and discovered that he's an ultra-powerful mage whose ability to turn his entire body into pure diamond (hence his name) has allowed him to journey to space and other inhospitable environments. Through the vast knowledge he's acquired during his explorations, he's also become somewhat of a renowned weapons creator and arms dealer.
The Glimmer Man has landed in Masteria looking for something called White Versal Materia, a rare element from the alternate dimension of Versal he's been dying to experiment with. To thank me for recovering some and bringing it to him, he's promised to make me a weapon of my own from it. However, I've got to also track down 7 Black Crystals and return these to him as well. Only then can he reduce the naturally unstable Materia down to a useable form. A weapon made from an otherwordly material! I wonder what it does...