In the shaman X description it states that when gaining this ability, you get to pick traits from a single sphere.
Now:
- Does gaining this ability multiple times work?
- Do you need to re-select the same sphere every time you get this ability or can you select different spheres for each instance of Shaman X?
- Lastly, does it work when you get Shaman X from different branches (like the Shamanism branch, and the Moon region branch)?
- Can you select opposed spheres for different Shaman X instances?
I believe the answers are yes, technically yes, yes and no.
Abilities of the same name stack. This is how Increases and Enhancements work; they are Abilities that are specifically limited by Branches of Life and/or the Maximum Age Bonus. All other Abilities are not limited in this way, although they may be restricted by their own rules, or those of their source(s).
What this means for Shaman is that all instances of [Shaman X] on a Species and/or Class are combining into a single Shaman Ability. If you were to take [Shamans] from the Moon Region, followed by [Shamanism] and [Elder Shaman] from the Shamanism Spiritual and Scientific Knowledge Branch, you'd end up with a hefty [Shaman 5] after all was said and done. All of the ensuing Bonus Traits would have to be taken from the same Sphere of Influence, but that'd be a mighty Class indeed.
Lastly, as stated elsewhere, Opposing Spheres don't seem to have any real effect. Usually the subjects are on one side of the Light/Darkness divide, and so cannot be taken by the other side regardless.