Your first few matches are against a computer opponent while you learn the game.
After that, Duel looks for another player who is searching for a match at a similar table at the same time. If nobody is available within a few seconds, you play against a computer opponent instead. Computer opponents have a name and an avatar like everyone else, so you may not be able to tell which one you got.
After those first matches, the dice for both players in the Gameroom are rolled on our server.