The Dark Energy Survey is carrying out a 5-year survey of one-eighth of the sky using the 4-meter Blanco telescope in Chile and its state-of-the-art 570 Mpix camera, DECam. Though this dataset was primarily envisioned for cosmology and extragalactic science, our University of Michigan group has developed it into a powerful tool to study the solar system beyond Neptune. The hundreds of new objects we've discovered include a dwarf-planet-sized object at nearly three times Pluto's distance, and several "extreme trans-Neptunian objects" whose orbits may hint at the presence of a ~10 earth-mass ninth planet. I'll discuss these discoveries in our own cosmic back yard, and their implications for what may lie beyond.