Moon cycle was the term used to refer to a woman's menstrual cycle, with the blood being known as moon blood. Kahlan was experiencing her moon cycle for most of the events of Temple of the Winds, which was later revealed to be a possible element in a prophecy predicting Kahlan's presumed betrayal of Richard. Additionally, Cara was advised by an herbalist to mix her 'moon blood' into an ointment used to treat Richard's skin while it was itching because of the mriswith cape. Just as with any other blood in the Sword of Truth universe, moon blood was assumed to have particular magical significance. Whether or not this was particularly accurate in the case of the moon blood is unknown, though Richard simply considered it a disgusting superstition. Indeed, he was revolted when he found out what was really in Cara's healing ointment and wished that Cara hadn't mentioned it.