Gusty the Great is the posthumous overarching protagonist of My Little Pony: Friendship is Magic. She was a legendary hero and the one who led her Unicorn Warriors to defeat the villainous Grogar.
Gusty was a white unicorn with a green mane and tail with a red streak. Her cutie mark consists of leaves blowing in the wind.
Personality
Gusty was quite brave as she stood up to Grogar, who was a powerful and terrifying tyrant at the time, alongside some other unicorns.
Abilities and Powers
As a unicorn, Gusty was able to use magic with her horn, but the extent of her magic was unknown. Considering her cutie-mark, she was likely adept at using wind magic. She was also cunning as she came up with a plan to take "Grogar"'s source of power away from him.
History
Legend
Thousands of years ago, long before the pony tribes united as one, the country that would be known as Equestria was a dark and forboding land where horrible monsters created by the evil emperor Grogar terrorized the populace so that they could fuel their creator's power with their fear. He also occaiosnally used his Bewitching Bell, which was the source of Grogar's power, to steal magic from unicorns to energize himself using his. But then a brave unicorn named Gusty the Great rose up alongside her Unicorn Warriors to challenge him.
They encountered Grogar atop the hill that would lead to Cloudsdale; The Unicorn Warriors shot magical beams into the clouds and wrapped around Grogar and pulled him to the ground, but the evil goat manages to break through the bonds as fear gave him power. The rest of the battle was unknown, but it was confirmed that she managed to steal away the Bewitching Bell and banished him from the land, never to return. Afterwards, Gusty hid the bell within an enchanted cave atop Mount Everhoof, which was protected by a powerful forcefield and magical winds to prevent anycreature from getting to it.
Legacy
The story of Gusty's triumph over Grogar was told for generations, lasting over thousands of years. Princess Twilight Sparkle was seen telling the story to some sick foals in Ponyville Hospital.
Eventually, after many millennia, Discord disguised himself as Grogar to gather the most sinister villains in the kingdom to turn them into formidable opponents to make Twilight confident enough to be the ruler of Equestria. In order to teach them about teamwork, he sent them on a mission to retrieve Grogar's bell from its resting place, and they eventually did after finally learning to cooperate. However, they then use the bell to take Discord's magic and expose him, forcing him to leave the lair so that they can rule over Equestria themselves.
Trivia
Considering that this was long before Equestria was established, she may have had some prejudice against pegasi and earth ponies, since her team consisted only of unicorns.