If you couldn't tell from me deleting the old princess drawings.. I still haven't found a battery, so I decided to do headcanons for the two of them! I have LOOOOOOTS for Luna and Celestia, but I'll only cover the things I find the most interesting, unless people want more. Nightmare Moon will be included here too for simplicity's sake.

- Luna has never had any romantic attraction towards anyone. She is aro/ace.

- Luna's power and appearance is based on the phases of the moon. As the moon becomes closer to full, her power over the real world is strengthened. Her hair also starts to turn silver, and it's nearly reflective.

- Luna can predict the future extremely accurately, though she hadn't figured it out until she was banished to the moon. You have a lot of time to think about things when you're banished for 1000 years. She still has a habit of dismissing her premonitions, even when they could be extremely useful.

- After Luna was freed from Nightmare Moon, Celestia sent her to spend time with the mane six to learn how to reintegrate with society. I will probably do a post about this, since there are quite a few details.

- When Princess Luna was banished to the moon, she was placed in an 'eternal slumber.' However, being the Princess of Dreams, this didn't go quite as originally intended. As the moon changed phases, so did Luna's power over the dream realm and thus as her powers grew stronger, she was able to pull herself out of her dreams and gain awareness, sort of like a lucid dream. She spent most of the full moons plotting her revenge or pleading for Celestia to take her back.

-Luna plays the harp and was able to continue practicing it during her banishment on the moon, so she's probably one of the best lyre/harp players out there. It is said that her music can soothe even the most troubled minds and relax any creature until they fall to sleep.

- Luna is magically stronger than her sister. It took longer for her powers to emerge to their full potential, though.

- Luna has created each and every constellation in the night sky. Some are dedicated to old friends who passed away, and some are simply her just having fun. Each night she painstakingly makes sure each star is in its proper position. While banished to the moon, her sister was simply unable to raise the stars to their proper position. Now that she has returned, Luna filled the night skies with constellations once more.

- The moon isn't referred to as 'the moon'. Instead, it is 'her moon'. This practice started after Nightmare Moon's banishment, and thus "her moon" referred to Celestia and not Luna. In the present day, though, it has come to mean Luna's moon. Similarly, the stars are also referred to as 'her stars', though her stars never once referred to Celestia. It is said the followers of Nightmare Moon kept it alive.

- Luna can see ghosts. She can also help soothe them so they rest peacefully. While she was banished, lots of ghosts were unable to rest properly and thus rumors of Nightmare Moon leaving behind dark magic were started. While this was partially true, it was nowhere near on the level of what ponies rumored.

- Nightmare Moon's name used to be seen as a curse- speaking her name was said to doom the speaker to nightmares for the rest of their lives.. though this was not true. This is also the reason why nopony knew about Nightmare Moon, and only The Mare in The Moon.

- Seeing Luna as a representation for the future in a Hearth's Warming Tail isn't wild. Since she is in control of her moon, and thus one of the main sources of time telling, she's come to represent the passage of time according to some ponies, mainly those who lived before Nightmare Moon.

- Nightmare Moon is incredibly cold and has an air around her that can freeze water and leave frost on windows. In fact, there is a layer of frost on her armor, her wings, her horn, and even her eyelashes. It only grew more intense when banished to the moon.

Aand that's pretty much the basics! I've left a few things out that I'll cover in Celestia's bio!