In advancement there are two well-defined areas of improvement, and then there are… Extras.
Extras are for everything that doesn’t fit into the Skill or Trait categories, though they cannot step on the toes of whatever is set up as the special category. In The Carrington Event, they should not be Eldritch Powers, and in Starscape, where Psionics is a Key Power, they cannot be psionic powers even though such powers exist in the setting.
Extras basically are anything that doesn’t fit in the rest of the game mechanics. It’s common for a player character to want a mansion or some social power ad prestige – you can represent that with an Extra. Extras should not interfere with the Skill and Traits systems, and are not meant to be powerful. This simply allow a player to define their character better.
Sometimes an Extra does grant a usable benefit – if so, give them a checkbox to represent that benefit can be used, say once per adventure.
Exactly what extras are and what they can do will vary with the campaign, and may need to be explored through playtesting.
