Rupert of Hentzau is a more dangerous adversary than Black Michael. This is why he lives to fight another day at the end of The Prisoner of Zenda and is the principal (and eponymous) antagonist in its sequel. Rudolf Rassendyll says that Michael has many qualities, but he never describes what they are and the reader is left with an impression of a sullen and vengeful villain. Rupert, on the other hand, is shown to be exceptionally courageous and daring. Rassendyll seems even to have a sneaking affection for him, despite his evil nature. He comments:

For my part, if a man must needs be a knave, I would have him a debonair knave, and I liked Rupert Hentzau better than his long-faced, close-eyed companions. It makes your sin no worse, as I conceive, to do it a la mode and stylishly.

Rupert and Michael are equally devilish, but Rupert's exceptional courage and intelligence render him much more dangerous. He understands Rassendyll far better than Michael does, making him able to predict how he will act and react:

“The duke offers you more than I would,” he growled. “A halter for you, sire, was my suggestion. But he offers you safe-conduct across the frontier and a million crowns.”

“I prefer your offer, my lord, if I am bound to one.”

“You refuse?”

“Of course.”

“I told Michael you would;” and the villain, his temper restored, gave me the sunniest of smiles. “The fact is, between ourselves,” he continued, “Michael doesn’t understand a gentleman.”