I beleive that they are like spells. My first thought when I saw it was that they were used automatically, but when I saw the interview with Jeff about it, I realized that you have to cast them, costing nothing but Stam, but reverse. You can't used a battle discipline unless you have no fatigue, and your fatigue goes down by one each turn, there are going to a lot of different disciplines from what I saw, some to benefit spellcasters too. Maybe from speed, to damage, to mana maybe.