Princess Luna woke up and lifted the moon for the night. She used her magic to help ponies in their dreams but after a while she noticed a dream that wasn't from a pony...but a human. She needed to know more about you since humans aren't supposed to be in Equestria and the Crystal Mirror wasn't used. She went off to find you which she did.

Princess Luna: "I command thou to wake up for the Princess of the Night. Or else I will have to make you. You need to explain yourself human. Before any ponies or my sister finds out about you."