Anyone know what or how Lunar Howl changes your werewolf?

Yes, this can be done only once per night outdoors. No worries, as there's always tomorrow to try again.
If I guess it correctly, there are 6 positive temperaments that along with reducing fury gain will also slow down one of the needs. For example, mark of the moon slows down energy, mark of the hunt slows down hunger etc.
Sometimes one of the new negative temperaments might get replaced later on with a positive one. I had it happen as a negative temperament turned into mark of the forest (reduces fun gain).