After Luna's purging of Nightmare moon, times were tough on her despite her warm reception from her older sister. She studies the history she's missed since her imprisonment. Through all that has happened she begins to see the compassion and the love of her people, given in time. She cannot allow such acts of kindness the harmonious ponies she governs over to be unnoticed.  With the intense emotion she feels, she wants to grant a gift to all her ponies as she makes a pledge.