[ She probably should have expected that question. Saber pauses, as if figuring out how to phrase her answer. ]

No one forces you, but... it becomes difficult to control one's self around the full moon, if you are a "monster". You might lose yourself in madness and go completely wild. Or if you are a mage or witch, you might find the build-up of mana too much for your body to bear.

[ She frowns. ]

The loss of control is not pleasant.