Lightning Dash

Lightning Dash is the twin of Rainbow Dash. She was created by Starlight Glimmer so she doesn't have a decided cutie mark. Her cutie mark changes when her emotion/feeling changes. She was created a long time ago when Starlight didn't have anypony in her utopian village. When one villager came, Starlight thought she didn't need Lightning and the other evil twins anymore and banished them to galaxy. There they learned nothing and after the villagers regained their cutie marks, Starlight got angry and lifted their banishment and taught them that evil was the only way to be relaxing. Lightning followed and got nicer each day, and finally she thought evil was not relaxing, and she would get plenty of punishments from that. She then protested that she didn't need to follow what Starlight says even thought she created them, the other twins argued but Midnight Glimmer kept quiet. Lightning stared at the four, shocked. She protested again. Everypony else agreed.

Personality
She is evil at first, but as the journeys went on, she becomes nicer. She loves freedom.