Steve Jackson Games Munchkin Adventurers in Training Dice Pack
This dice pack includes three custom pearlized 19mm Munchkin-head dice in green, purple, and black, as well as two purple 16mm d6's.
And there's a RULE!
Rule: The smaller purple dice are Adventurers in Training. When you roll to Run Away, roll both one of the larger dice and one of the smaller purple dice. If you fail your Run Away roll on the larger die and the result on the smaller die is lower, you can sacrifice your trainee to the monster and escape anyway. Put the smaller die back in the box; it's out of this game.