While previous adventures set within the world of the X-Men have dealt with the concept of physical abilities (healing factors, laser vision, lightning, etc.)
Legion will place its focus on more cerebral powers of the mutant world.
The basic idea behind these characters’ powers has been explained before, but this is undoubtedly the clearest explanation we have received so far.
In short, it will be an examination of mind over might, which makes sense for a show that’s about the son of the similarly cerebral Charles Xavier.