Ben 10 The Mystery of the Mayan Sword. Join Ben 10, Gwen, and Grandpa Max as they try to stop the Forever Knights from getting their hands on The Mystery of the Mayan Sword! Which legends says it is the most dangerous weapon on the planet. Search for clues, solve puzzles, and explore four epic levels as you prevent the Forever Knights from attaining this weapon of mass destruction! Along the way you’ll be transforming into your favorite aliens like Grey Matter, Stinkfly, and Four Arms. Play more cartoon games on RoundGames. Enjoy and have fun in playing this free online game. Good luck.