DUEL2, formerly DuelMasters, is a turn-base, Play-By-Mail game run by Reality Simulations, Inc. (RSI) out of Tempe, Arizona, where players, called managers, design and run up to five warriors per team against other managers. The game is one of the longest running Play-By-Mail games still operating. It has been cited by Greg Lindahl's PBM page as one that is most talked about and has been a standard against which other gladiatorial PBM games have been measured. It is credited with inspiring at least one online gladiator game called Gladiator.