According to the peace of 89, Decebalus became a client king of Rome receiving money, craftsmen and war machines from the Roman Empire, to defend the empire’s borders. Undoubtedly this would have included the fearsome Scorpio that the Roman armies used so affectively. Instead of using the money as Rome intended, Decebalus decided to build new citadels in the mountains and to reinforce the already existing ones. This was the main reason for the following Roman attack under Emperor Trajan.
You can add these great warmachines into your Dacian armies.