"Promised Sands uses the Trinary System. This easy to use, fast resolution mechanic requires only three ten-sided dice to play. (You might like to have one of each size for character generation, however.)"
The Tinary System always uses three 10-sided dice. Two of these are percentile dice (01-100) - compared to the required Success Value, these dice determine the success or failure of an action. The third die is the Effect Die (1-10).