A mare named Blaze Firestarter comes to Ponyville and immediately befriends Lightning Dust, Rainbow Dash and Spitfire. She also starts at the Wonderbolts Academy.
Blaze seems to be a normal mare until she begins to do things very few can. She can tell how a pony is feeling just by making eye contact and she's better than Applejack on spotting a liar.
Twilight, Applejack and Starlight begins to think she's hiding something from them, but finding the truth about Blaze proves to be way more difficult than they expected.

Blaze Firestarter:
Personality: Bold, selfless, empathetic, cheerful and a little impish.

Good traits: Born leader, athletic, empathetic and loyal.
Bad traits: Explosive temper (literally) and impatient (at times).

Cutie mark: A Phoenix surrounded by a fire circle.

Bio: The only thing known about about Blaze is that her mane shows how she feels. When the mane looks normal she is either: Happy or feeling neutral. When the mane falls completely down and dims in colour she is sad. When her mane is moving around like a dim flame she is angry, when her mane moves like a bonfire she is furious and when it literally bursts into flames........well......I won't tell.

Design: A mixture of Starlight, Spitfire and Cadence's design. Her mane and tail is nearly identical to Starlight's, her colours (except her iris and coat) is mostly the same as Spitfire and her overall design (except the mane and tail) is the same as Cadence.

Warning: Some ponies burn to death

Big thanks to LSTS Connor for helping me improve the chapters before publishing.