User blog comment:JmLyan/Misya, the Moon Princess/@comment-5686533-20131129213235/@comment-7481207-20131129213758

The passive basically means that if you don't switch moon phase yourself for 10 seconds, it does it automatically and grants a small "stance activation" effect. It switches in the order Waning -> New -> Waxing -> Waning etc. Full Moon switches to the phase after the one she had when she used Full Moon (forgot that part and will edit it in).