Multiple green orbs of light moved randomly on a hillside.A friend and I were driving away from Devil's Tower NP approaching Devil's Tower Junction. It was very dark with no other sources of light or other cars nearby. At the same time, we both saw multiple orbs of green light frantically moving around in a seemingly random fashion on an embankment on the opposite side of the road, just a few feet from us. My friend who was not driving saw them for about ten seconds, while I only got a few 1 or 2 second glances. We turned around and searched the area and did not find anything at all unusual.