This might have happened. The Cimbri are still remembered by the old district name Himmerland. Plutarch describes the battle at Vercellae, which took place 101 B.C., and its immediate aftermath. Other classical writers, such as Tacitus and Strabo, and a treasure of archeological material enable us to guess at the Cimbri themselves. Apparently they were a Germanic tribe from Jutland, with some elements of Celtic culture; by the time they reached Italy they had grown into a formidable confederation.
King Mithradates the Great (more commonly but less correctly spelled Mithridates) is, of course, also historical. His expedition into Galatia in 100 B.C. is not mentioned by the scanty surviving records; but it is known that he had already fought with that strange kingdom and annexed some of its territory, so border trouble followed by a punitive sweep down past Ancyra is quite plausible.
At that time the area now called southern Russia was dominated by the Alanic tribes, among whom the Rukh-Ansa were prominent. They are presumably identical with the "Rhoxolani" whom Mithradates' general Diophantus defeated at the Crimea about 100 B.C.
The tradition described in the epilogue may be found in the thirteenth-century Heimskringlaand, in a different form, in the chronicle of Saxo Grammaticus.
Otherwise my sources are the usual ancient and modern ones. I have tried to keep the framework of verifiable historical fact accurate. For whatever brutality, licentiousness and unreasonable prejudice is shown by the people concerned, I apologize, adding only that by the standards of the modern free world the era was a good deal worse than I care to describe explicitly.
For the sake of connotation, cities and other political units are generally referred to by their classical rather than contemporary names. It should be obvious from context where any particular spot lies on the map. However, the following list of geographical equivalents may be found interesting.
Ancyra: Ankara, Turkey
Aquitania: West central France
Arausio: Orange, France
Asia: In ordinary Roman usage, the modern Asia Minor plus India
Byzantium: Istanbul, Turkey
Cimberland: Himmerland, northern Jutland, Denmark
Cimmerian Bosporus: A Greek kingdom in the Crimea
Colchis: Mingrelian Georgia, U.S.S.R.
Galatia: Central Turkey
Halys River: Kizil River, Turkey
Macedonia: Northern Greece
Narbonensis: Provence, i.e., southern France
Noreia: Near Vienna, Austria
Parthian Empire: Iran and Iraq
Pontus: Eastern half of northern Turkish coast, and southward
Sinope: Sinop, Turkey
Tauric Chersonese: The Crimea
Trapezus: Trabzon, Turkey (medieval Trebizond)
Vercellae: Vercelli, Italy, between Turin and Milan