A measure of your ability to protect yourself from psychological trauma, stay focused on your goals and actions despite distractions, and control your emotions.
Discipline determines a character’s hunger stress track (if they possess one) and is one of the three cornerstone skills for effective spellcasting, along with Conviction and Lore.
Discipline and Conviction partner together to represent your overall “fortress of the mind.” With both rated highly, you are rarely affected by emotional and psychic attacks (thanks to strong defense rolls from Discipline) and, when affected, you can take more psychological distress before you start to break down (thanks to the extra mental stress boxes from Conviction). When your Discipline and Conviction skills are not in line with each other, you may be easily affected by distress but have the kind of faith and confidence necessary to persevere despite that (low Discipline, high Conviction), or you may be very good at “compartmentalizing” your response to things but actually pretty fragile inside (high Discipline, low Conviction).
Use Discipline to keep focused a particular task or idea in circumstances where unusual concentration is necessary. The GM may ask that Discipline be used to restrict (page 214) skills being used in tense situations, representing a small penalty if you are not skilled at keeping your focus.
Use Discipline to master your own emotions. This could be as a defense against an Intimidation attack or keeping your terror in check in order to avoid feeding the fear-eating monster right next to you.
Use Discipline as the default skill for defense whenever something tries to deal mental stress to you or tries to mentally or psychologically assault you. At minimum, roll Discipline as the defense against certain Intimidation attacks, as well as against invasive mind magic.
Calm Blue Ocean: You are skilled at keeping your emotions in check. Gain +2 to Discipline when rolling to keep emotions under control.
Supreme Concentration: Your Discipline is considered to be Fantastic whenever Discipline would restrict, complement, or otherwise modify (page 214) another skill. This has no effect on your actual Discipline rating when the skill itself is being rolled.
Unshakable: When defending against social or mental attacks with Discipline, any of your aspects (such as consequences or other temporary or permanent aspects) that get tagged provide only a +1. If the attacker chooses to tag for a re-roll, you may “lock down” one of his dice, leaving him only the other three to re-roll.