Casting Spells
When a player casts a spell, they describe the effects they would like it to have. Nothing is impossible. As a spell is described, the GM will produce a DC for it, and decide which discipline(s) it falls under.
When the DC is exceeded by five points or more, the spell costs no Capacity. If you exceed by fewer than five, the spell costs the difference in Capacity. For example, if the DC for a spell is 25 and you roll a 30, the spell costs nothing, whereas if you roll a 27, it costs three Capacity. If you succeed in casting a spell but do not have sufficient capacity to cast it, the cost is deducted as 4 times the difference in HP (unless otherwise mentioned).
Failure
Spells that fail have a 50% chance to do nothing, and a 50% chance to be cast anyways, but act unpredictably. The more it is failed by the more unpredictably it acts - a failure of one or two points means it will be roughly the same, but the wildness increases exponentially the more it is failed. No matter what the Capacity is spent. For example, a spell with a DC of 25 failed with a roll of 20 costs 10 capacity.
Determining DC
Casting Time
Spells usually cost 4 AP to cast, but there may be exceptions.