I think I can guess without even checking in game.
***************SPOILER ALERT*******************
-$$$$$- Deleted Patch Notes - Beta 0.524 -$$$$$-
-At civ level 70 players will unlock 'Windball'.
-Many players have been asking for a minigame to help break up the pace of the game.
-Players must build a 'Windball Stadium' in their settlement. Windball can then be accessed by speaking to the Hearthstone.
-Players can those choose to challenge the local Overlord to a match. The Hearthstone will give the full list of rules in game, however in brief:
-Players must have atleast 12 NPCs with 50 Time Units available to form their starting line up.
-Before the first match players must choose a team uniform. A range of colours, fabrics and styles are available. Team morale is negatively affected by floral and polka dot designs, players are advised to choose wisely.
-A team mascot must be chosen. There are a variety of men dressed as animals from a range of time periods to choose from, again, certain choices will negatively affect team morale.
-Once confirmed, the player will then be taken to the Windball Pitch screen and the match will begin.
Note: The Overlords of the world take Windball very seriously, they are likely to field their strongest line up of Lieutenants, be prepeared! Losing a match will reduce moral for all NPCs in your settlement. Winning a match is likely to cause the Overlord to 'blame the ref' in a fit of frustration, at which point his team will riot in your settlement before leaving, killing most of your NPCs.
