From the announcement:
In 1978, legendary boxer Muhammad Ali proved that he truly was the Greatest of All Time by defeating the strongest man on Earth – Superman – in the pages of DC Comics’ historic Superman vs. Muhammad Ali issue. Far from a grudge match, this battle would ultimately set the two up to save the planet from an alien invasion, ending in the proclamation “WE are the greatest!”
Players will be able to purchase this commemorative set in the U.S. for the first time at the 2017 WizKids U.S. National and World Championships, this June.
This year’s events will be bigger than ever and WizKids will be offering even more incentives for players to come out and compete. Players can prepare for the biggest WizKids gaming events of the year by attending a WizKids Open Regional Championship and earning a National Championship Qualification in HeroClix or Dice Masters. More details on specific dates and locations of upcoming championships will be announced soon, so keep a look out for more information on the WizKids Info Network.