Onyx Stone
From MHWiki
The Onyx Stone is dropped by the Master of the Dojo Mouse in the Pinnacle Chamber and is used in the crafting of the Arcane Capturing Rod Of Never Yielding Mystery.
Description
Argued to be the source of power for the Masters of the Dojo, this magical stone is extremely rare and valuable. The stone seems to not have a clear use. Perhaps its purpose will be revealed eventually...