Sorry if this has already been posted, but I feel like I'm missing something in the rulebook and would appreciate some pointers.
In the description of psychic disciplines (p.164), the rulebook says that it is much harder to learn powers from different disciplines than it is to focus on one single discipline. However, there doesn't seem to be any game mechanic accounting for this, except for the one that says if you've mastered ten powers in one discipline you can reduce the PT by 5 when using any of those powers.
Is there anywhere where it states that a psyker must choose a particular discipline and what the consequences of that decision are?
Cheers,
Steve