闇の大結晶 [yami no ookesshou] or 'large crystallization of darkness' in Japanese.
Brave Exvius

Buy: - (sell: ? gil)
Gather: Demon Woods, Corobos Wetlands, Corobos Reef
Use: Mage's Hat, Ninja Gear, Biora
Type: Material, Number: 016
Description: A crystallization bearing an uncommonly strong power of darkness within
Profile: A large crystallization born of condensed Dark element magick power. It's used for many things, such as refining Dark element magicks, and in smithing and mixing. The crystal is filled to the brim with a deep darkness, and drains light from its surroundings. Because of that, should you place one in a room it can feel darker than usually. Since they're formed in darkness, it's difficult to find high quality ones.
Category: Item