Ehhhh... I seriously doubt that. The Void and voidsent eat up aether, not produce it in great enough quantity and quality that it can be compacted into a solid tangible substance. Unless a "void crystal" is anti-aether... but going by the laws of antimatter it would cease to exist almost immediately, not from someone touching it but just by coming into contact with normal aether. Which is in everything.
Going by previous games, the Warriors of Darkness should be either collecting or protecting the Crystals of Darkness. My money's on the former based on the patch title, assuming that's what they're doing, but without more information I don't want to make a judgment either way.