The Epsilon Account by Joni Parker

Thousands of years ago, Eledon was created for the Elves by their Mentors when they were forced to leave Earth. At least, that’s how the legend goes. In return, the Elves must pay them a tribute in gold, known as the Golden Harvest, every four thousand years. The Elfin Council of Elders appoints Lady Alexin (Alex) Dumwalt, the Keeper of the Keys, to manage the next payment, due 244 years from now. That is, until the Mentors show up unexpectedly and demand immediate payment of the Epsilon Account. Since the Harvest has never been called that, Alex suspects foul play and uncovers a sinister plot by the Star Elves, a rival clan from the Constellations, who want to steal the gold. To make matters worse, they're willing to do anything to succeed to include murder. Can Alex stop them and save the Elfin gold before it’s too late?