Nicholas Free of Impact X created an in-depth campaign for Legion. Without going into too much detail here you can read more about the Gathering Legion Campaign here.
In addition to that he also write two companion pieces going into further depth on how to create Hero characters:
He writes: “I was getting multiple questions about how heroic units work so i wrote up a quick tutorial and simplified how increasing or decreasing surges work.
for those of you who haven’t seen yet, I made a pretty robust campaign league play supplement. We are still streamlining it and working out the kinks as a community – so take a look and share your thoughts.
after the character development framework is solid we’re going to add campaign specific mission cards.”
Gathering Legions: How To Build Your Own Heroic Commander or Operative
Legion HoloNet 