In Diablo 2, thief is a special monster ability that allows the enemy to cause you to drop potions from your belt (the next potion in lines falls into the next place normally). Very few monster had this rare, difficult ability, most notably Lord De Seis, one of the last enemies vefore Diablo. There were so many bugs and crashes associated with this power, that is was taken out of the game alltogether in version 1.04. The potions would fall at your feet, but in the heat of a fast, loaded battle, you could find yourself without a healing aid at a critical moment.