How much could Princess Luna love another pony?
How much would she endure to allow her lover to achieve their ambitions?
Even she did not know how much she would fall in love until she was one with the Element of Loyalty herself.

This can be read as a one-shot or continued to its sequel The Setting of the Moon, when the relationship between Princess Luna and Rainbow Dash is pushed to its limits. Caution, this sequel is T rated.