Luna was raised in the shadow that Celestia cast. That was ok, she really didn't mind at first. Slowly, over the years the light got brighter and the shadow longer. Until, it all became too much.
Cadence is stressed out, she has an alicorn baby to raise. Just when she thought the situation couldn't get any worse, she is called upon to solve a problem of love. Discord and Sombra's love problem.