Cryptic Alliances was a fun idea in Gamma World. It should be brought into Mutant Future. It gives the characters a reason for meeting, travelling together, and golas to aim for. A common purpose. Though there is nothing wrong with a character from a different group, publicly or in secret. (spy?)
My favorite was the Crusaders or Friends of Justice.
Friends of Justice (Crusaders) –( Superheroes)
Someone found an Old World comic book and got an idea......
These beings have been chosen by extraordinary powers just like heroes before the apocalypse to fight for truth and justice. Some are very effective protectors some die fairly quickly. Anyone with skills, who submits to the hero oath and has the might to survive is welcome to join as a hero. Artist members record and tell of their deeds with crude picture stories and figurines which are collected by fans across the wasteland. Fan rank members are very common and some control shrines to the heroes of the ancients. Cult heroes wear colourful uniforms
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Feel free to post your ideas for a Cryptic Alliance.