Originally posted by metalhead
Not necessarily. Many empires successfully employed mercenaries, and incorporated them into their armies as regular units. Hell, the Byzantines had used mercenary fighting forces for practically their entire existence. And while the Varangian Guard were employed in the second half of the Byzantine Empire's existence, they witnessed it in glory before they had to see its decline. The exact kataphraktoi employed by the Byzantines surely had its own unique characteristics - but the Varangian Guard were certainly much more unique, and therefore, I think, better suited as a UU.