The second part in the 1284 Book of Games of Alfonso X. contains the description of twelve medieval games of dice. Certain information on the amount and timing of bets of the players are only very briefly displayed and are completely missing in several games. The exact course of such games is therefore unknown. What did the players know about their chances of rolling dice and how they could use them when playing the dice? In order to imagine the process of betting for gain, the characteristics of these games of dice are examined and compared with contemporary games of chance.