Twilight Sparkle.

Twilight Sparkle is a studious unicorn from Canterlot and the holder of the Element of Magic. At the beginning of My Little Pony: Friendship is Magic she moved to Ponyville on the orders of Princess Celestia and has been living there ever since. She resides in the Books and Branches library As Celestia's personal student, she has been tasked to stay with her friends and write reports about lessons in friendship. She arguably is the most central character in Friendship is Magic and in the Cutie Mark Clash.

Move List
Twilight's attacks are directly inspired by the Street Fighter character Ryu.

Back-story
Twilight started off as an ambitious filly in Canterlot, studying hard to get into Magic School and impress Princess Celestia. During her exam for entry into the school, she almost couldn't hatch Spike's egg until filly Rainbow Dash's Sonic Rainboom interrupted her and caused a strong magical reaction. Her magic turned out to be very potent and hard to control until Celestia herself intervened and calmed Twilight down. Celestia was so impressed by the display that she invited Twilight to be her personal student, pointing out the filly's new Cutie Mark. Twilight agreed very eagerly. Years later, Twilight has grown into a dedicated student, albeit anti-social, with the baby dragon Spike as her assistant. Twilight began investigating the legend of the Mare in the Moon only for Celestia to tell her to go to Ponyville to check preparations for the Summer Sun Celebration and to "make some friends." Her mind set to her task makes it difficult for her to truly make any friends at first. When Nightmare Moon returned, she was forced to travel with with Applejack, Fluttershy, Rainbow Dash, Rarity, and Pinkie Pie, to find the Elements of Harmony. During her travels, she befriends the other ponies and comes to realize they all represent the Elements with herself as the Element of Magic. After vanquishing Nightmare Moon, Twilight asks to stay with her friends in Ponyville. Celestia agrees to this arrangement on the condition that Twilight send weekly reports detailing the student's findings on the magic of friendship.

Twilight has since stayed in Ponyville, participating (with wildly varying degrees of glee) in the local culture and helping the community wherever she can. She can also be something of an egghead.

Personality
In general, Twilight is a very friendly and helpful pony. Moving to Ponyville has made her much more outgoing, as she's always part of something big going on in town. Despite this, she is still charmingly naive when it comes to social matters, such as a sleepover. She'll follow up on this naivete with her belief that she can learn about anything from a book and attempt to follow a book to the letter. This is one of the many instances in which she turns out to be very animated with her emotions, especially during intense situations. She relies so much on logic and facts that she is quickly skeptical of anything that logic or science cannot explain. This is most apparent when dealing with Pinkie Pie. Pinkie's general carefree attitude can bother Twilight sometimes, but not as much as her supernatural "Pinkie Senses." Twilight denies the Pinkie Senses to the point of violent rage, but eventually comes to accept it, showing she is still open to concepts and ideas beyond her own understanding. Despite being perhaps the most adept magic-user in all of Ponyville, Twilight is humble about it. She doesn't think about her abilities much and even goes out of her way to avoid making a big deal out of it. On the other hand, she's so practical about it that she may be at a loss for what to do without her magic.

Abilities
Being a unicorn, Twilight is able to use magic in several forms. At one point, she demonstrated the ability to perform at least 25 tricks. The most common use is in levitating objects, sometimes dozens of small objects at one time, with great precision. Heavier or live targets require greater effort. Other abilities include but are not limited to generating wind, stopping flying pegasi, being able to alter the minds of parasprites, growing mustaches, and making an object appear irresistable.

Campaign
Twilight was the last of the Mane Six to sign up for the Cutie Mark Clash since she didn't have any good reason to do so. By the end of Chapter 1 the rest of the six had joined for their assorted reasons and convinced Twilight to join as well. Not one to turn down her friends, Twilight agreed to join, much to their delight (and apparently that of Lady Aremis). Twilight's first fight was thrust upon her by her first opponent, The Great and Powerful Trixie. She did not fight back well due to having only little practice with her fighting abilities, but managed to fight Trixie to a stand-still. The fight ended when Trixie forefit, apparently making a statement.

Since then, Twilight has made the most of the tournament by seeing it as an opportunity to do research. Unfortunately, she had started with the least predictable opponent, Pinkie Pie, who had been mimicking Street Fighter character Dan Hibiki at the time, and lost. Twilight took the loss well enough and continues the tournament in high spirits.