Trixie Lulamoon

Trixie Lulamoon is the main antagonist of "Boast Busters" and "Magic Duel". She is a female unicorn magician that claims she has better magic that Twilight Sparkle. In "Magic Duel", when she buys the Alicorn Amulet, she becomes overwhelmed with the power and challenges Twilight into a magic competition.

Trixie often refers to herself as "The Great and Powerful Trixie". She usually rolls the "r's" in words. Because of this, she speaks about herself in third-person form.

Appearance
Trixie's mane is composed of two different shades of blue: a light blue and a very pale blue. Her coat is another shade of blue, except it is darker than her mane. Her eyes are light violet fading into purple.

Her cutie mark is a sparkling blue moon with a magic wand on top, indicating that she is destined to be a magician.

Personality
Trixie is one who likes to boast to other ponies. In "Boast Busters", she claims that she can defeat an Ursa Major that was attacking Hoofington. When an Ursa Minor shows up, she screams in shock and runs away.

In Magic Duel, she becomes full of darkness when she is possessed by the Alicorn Amulet. At the end of the episode, she claims that she is "The Great and Apologetic Trixie" and runs off.

In the Equestria Girls I movie, she is meant to be funny when she suddenly says "The Great and Powerful Trixie!" and then says, "wants some peanut butter crackers". But in Rainbow Rocks, she falls under the Dazzlings' spell and argues that her band is the best and boasts about it.

Twilight Sparkle
They were in many fights and shows up at Twilight's castle when she becomes friends with Starlight.

The Pie Family
In "Magic Duel", it is revealed that after the episode "Boast Busters", she was humiliated and went to work at the former home of Pinkie Pie (the rock farm). She failed at using rocks as revealed in her magic aura.

Starlight Glimmer
Starlight is Trixie's first friend, and they have many things in common. They met at a salon.

When Trixie claims that she was using Starlight, Starlight left her and Trixie was miserable. She attempted the Manticore magic trick, hoping Starlight would assist her and forgive her.

Trivia

 * Twilight doesn't trust her until the end of "No Second Prances".