After reaching your profile to Level 5, you will be able to select Guilds on the main menu of Injustice 2. Here, you can either create or join your very our Guild. Guilds are where people from all around the world can team up to accomplish certain tasks as one, reaping the rewards as a group such as Mother Boxes. Guilds can be set as Free To Join, Open or Private, and you can actually search for a specific Guild by its ID Number.
There are even daily and weekly challenges that you can complete as a Guild, which will earn all players apart of such with Mothers Boxes, GP, and Guild Credits. Mother Boxes earn you certain gear for characters, netted by earning Trophies apart of these challenges; GP affects each players ranking on global leader boards; and Guild Credits are just like normal credits, ones that are allowed to be used to buy even more Mother Boxes. The more member you have on your Guild, the quicker you will finish challenges, and the more challenges you finish, the more rewards everyone will earn.