Certain mystic techniques such as warding and item creation require the mystic to spend sphere points on a semi-permanent basis. Spending points in this manner is called consuming them. When points are consumed, the sphere rank temporarily drops when the points are spent. The sphere rank returns to normal when certain conditions are met, depending on why the points were consumed. Note that even when the sphere ranks return, the spent points do not return until the mystic refills them using Reserve as normal.
For example, Leander the mystic wizard wishes to create an anklet that grants him an extra partial action each round. While creating the anklet, he consumes Enh 6 (the cost of the haste effect). Normally, he has nine ranks in Enhancement, but until the consumed points are returned to him (when the item is completed), he effectively has only three ranks. When he finishes the item, his ranks in Enhancement return to nine, but he still has only three Enhancement sphere points remaining, until he chooses to refill the sphere using Reserve.