The deal with Starlight Glimmer

[BrineBlade 28]

My thoughts...

 

 

Starlight was in the same Magic Kindergarten class as Twilight, and was the most powerful in the class until Twilight came along, which caused her to become jealous of Twilight. She then found later on that Twilght became Princess Celestia's student, furthering her jealousy, and thinking that she could've been Celestia's student, plans revenge. She studied darker magic secretly until she found a way to seperate a cutie mark from a pony. She figured that if she couldn't be special, then nobody could be. It was at that point that she got her cutie mark. It could also be the reason why she wanted everyone except for her to be the same, so she would feel special. It would also explain why she wanted to take the Mane 6s' marks away, not only taking revenge on Twilight, but also hoping to spread her way of order across Equestria.

 

It could also be why she wants to change the past so that none of the Mane 6 get their marks. That way she could possibly be Celestia's student and future Princess.