Not so apparent in this rough sketch, her eye lines should resemble that of Celestia.
As her cutiemark hints she can manipulate weather.
Leana is the name given by Celestia which roughly means "Daughter of the Sun".
Scootaloo was the name given her when she ended up in a foster home.
Her background is laced with tragedy, misunderstanding and even irrational fear.
Her horn appeared along with her cutie mark around her mid teen years though before that she started to outgrow both Sweetie Belle and Applebloom physically.
Only Nyx outgrew her in size eventually.
Reply on a post at FA regarding Scootaloos background Story.
"But why would a god give up their child? "
Nightmare Moon. (the second incident).
The Idea was to hide Leana with the father until that time.
Celestia broke her vows of abstinence and procreation and fell in love and mated with an extremely rare Pegasus pony who can cast spells Without a horn) and possesses weather control powers.
His name is Tempest a former rogue (Halcyon originally. Celestia's job is to stop him but after she found out why it is the way he is she felt empathy which eventually turned into love, mind you after years).
Celestia saw her blunder of mating during her Heat which eventually led to her being pregnant. However both she and Tempest decided to keep the baby despite possible public backlash of scandals.
Celestia even proposed going out in the open and marry.
As her belly grew in size due to her pregnancy she used a special type of illusion spell to look slim.
This spell however requires light but constant concentration (like holding up a pencil). When she's asleep it doesn't work. She manages to fool even Starshine Shimmer during that time.
Only Twilight Sparkle as a young filly saw a glimpse of Celestia distended belly when Celestia during one of her late night cravings gobbled up cake and left her guard down.
Seeing trouble ahead regarding the return of her Sister Celestia entrusted Tempest to hide Leana and at the same time Celestia used.
Celestia gave birth to Leana in the presence of Tempest in secrecy somewhere in Ever Free Forest. She stayed with her filly for a few weeks (while raising the sun and moon in that time).
Then it was decided to hide her precious filly with Tempest from Nightmare Moon for her eventual return.
Since Nightmare Moon possesses dream reading and manipulation powers information regarding her filly would not be safe even in her head.
To prepare for the worst case scenario Celestia by using her magic decided to (with the help of her lover) selectively erase her own memory of everything of her newborn daughter from conception to present.
Even down to the subconscious level which is an extremely dangerous procedure which if gone very wrong would have rendered Celestia a mental vegetable.
Tempest also proposed to selectively erase the memory of him.
When the danger of Nightmare Moon has passed and at an appointed agreed time Tempest would come out hiding and use a keyword and his magic to restore the missing memory.
It would have worked flawlessly hadn't one of a former enemy of Tempest during his rogue years decided to make an unexpected comeback.
Seeing that calling Celestia for help is out of the question since she wouldn't remember both him or her own daughter he decided to deal with this threat himself.
He hid his newborn filly in a Foster Home located in Manehatten and entrusted her to an old friend named Sandy who ran that home.
To ensure her safety even more he extracted some of his daughter's alicorn powers and with a powerful spell suppressed the existence of her horn making her look like a simple Pegasus filly
It was expected that his absence would be temporary and that he would collect his daughter after he dealt with this dangerous threat.
Unfortunately he never returned nor was seen again.
And with him gone there was no key word to restore Celestia's memory of her daughter and her lover even after the threat of Nighmare Moon has passed.
The spell he casts to make his daughter look like a pegasus lasted 15 years and drained him so much it may have doomed him when he faced his old enemy.
It isn't known what the fate is of Tempest