| “ | A magic gem filled with lightning. Fia found it buried at the Nelde Ruins. | ” |
The Thunder Onyx is an Event Item in Riviera: The Promised Land. It can be found in the Nelde Ruins stage.
Acquirement: Located in the third room of the Tree Ruins; examine the Rubble and have Fia search and she will find this ore.
Function: Trade it to Chappi along with all your swords and he'll forge a Thunder Blade x50.