Rinsitinium

Rinsitinium is a gem that holds a great energy inside of it. The known power of a single gem would be the equivalent to a dwarven furnace being burned throughout 4 months at full flame. Though it is incredibly powerful, the Dwarves hold the monopoly for the gem, being the sole inventor and sole user of the gems. Though the Dwarves have enough technology to ensure that the stone could not be used by any other race against them, there is an extremely limited price for using the gems. Legend has it that when one is obtained by another race, the screams of the Oread people come back from the land of the dead to destroy the stone and receive peace. Whether or not this is true has neither been confirmed nor denied.
The reason that the Rinsitinium is so limited is because the sole material needed in order to make it is through compressed and appropriately heated Oread corpses. Though the way that the element was discovered is entirely unknown, those who seek the stone are largely unsuccessful in trying to reproduce it due to lacking the necessary unique materials that are found in Oread bone structures. If one were to get a single gem from the Dwarves,

Inventor(s)

Unknown, though the most likely suspect would be a Dwarven mechanist or coroner