An ample writeup of this shadow can be found at http://www.dkcomm.net/rhea/AmberRPG/UnicornSeishi/BeyondGoldenCircle.html#Mystara on the official campaign site.
Home to the The Corunglain Free Rifle Company, Mystara was, during the Herald Crisis, the destination of many groups all involved in an effort to recover the spikards and the Dragon Staff once possessed by the now fallen Gaunt Man.
As it turned out, the Kuonji Ukyou had already managed to snag the Lion spikard, which he claimed to be safekeeping. And after a long and arduous struggle through a booby-trapped pyramid, the Amber contingent found that he'd also managed to swipe the Dragon spikard as well, having left a false spikard signature behind to make them waste time and effort to do so. This did not exactly endeared him to his relations or their friends; Keitaro in particular still hates his guts. The staff was likewise been recovered, taken from the hands of the Gaunt Man's henchman, Ancalgon?, and claimed as a prize by Beowulf, who wields it still.