The Epsilite Harvest.

The galaxy is full of worlds, and each world has a unique atmosphere, terrain, and minerals.  There are billions of minerals in the Galaxy, but there are few as powerful as epsilite.  Epsilite is only found on two known planets, Onsus Delta and Eridu.  Onsus Delta was destroyed in the Second Great War, Eridu is now the only known planet that holds this invaluable ore.  In 2634 AI, epsilite was found, deep within Eridu, miners from all over the galaxy came to the human homeworld, with great machines that burrowed down, generally from the arctic, miles deep, and found great caverns full of epsilite.  This was known as the Epsilite Harvest.  The epsilite harvest was twice as big as the Quantium Rush on Ius, the arctic was practically destroyed, the native wildlife were temporarily moved to the ice world of Tenva Prime, where the Yapas gladly watched over the exotic animals.  After about five years of mining, the Emperor banned the private prospecting of Epsilite, but mining corporations with Imperium-issued licenses can still mine the powerful mineral.  The Rodux System Mining Corporation is the leader in epsilite supply.  Epsilite in value is succeeded by Quantium, which is succeeded by Xullvelium (or Star Copper), which has been depleted for eons.