Twilight Sparkle arrived in this world to pursue Sunset Shimmer and reclaim the crown stolen from her world. Crossing via a dimensional portal into this world was a jarring event and a lot of adjustment as she went from a quadruped to a bipedal world. The fact that her baby dragon assistant, Spike, tagged along with her made it slightly easier. As she investigated she found that this world seemed to mirror the people she knew back in her dimension, despite the fact that science had taken the front seat instead of magic as in Equestria. With the help of doppelganger of her friends they retrieved her crown and successfully reformed Sunset Shimmer after a climactic battle. Returning home, she left her new friends to help Sunset understand the Magic of Friendship.
It didn’t take long for another threat to rise soom after as three Sirens, banished from Twilight’s world to this one, took notice of the battle
The Equestrian Magic that had depowered Sunset had left trace amounts of itself, restarting their powers. Using that magic, they slowly put Canterlot Highschool under their spell and planned to overtake everything and everyone at a Battle of the bands gathering.
Twilight quickly returned in the middle of the problem and soon worked to fix it, with the help of Sunset Shimmer and the rest of her friends. Things took a darker tone when feeling threatened by Sunset and her friends, the three Sirens cornered Sunset in a dark hallway and delivered a verbal and physical beating on the former student of Celestia.
Countering the Siren’s abilities with their own Magic of Friendship, the tide turned for Twilight and her friends at the Battle of the Bands. The Sirens counter-attacked and knocked Twilight and her friends down, closing in for the proverbial deathblow. Sunset Shimmer intervened despite feeling isolated and alone from her previous experiences with the school. The battle turned Sunset began to surge with power as she began to understand the Magic of Friendship!
However, as the Power of Friendship surged through her, the beatings she'd taken and her schoolmates indifference became too powerful inside her. Harnessing the raw energy she fired a massive blast of magic at the Sirens.
The dark magic that powered the Sirens powers collided with the raw magic like gasoline to a flame just as Twilight tried to call out to Sunset to stop.
The resulting explosion known as The Canterlot Disaster, caused most of those left alive with meta-human powers, though not all of them manifesting immediately.
Another casualty was the dimensional portal that led back to Sunset and Twilight’s home world, it was destroyed in the blast, trapping them both there in that dimension.
A great deal of adjustment was required by Twilight, dealing with survivor's guilt as well as having her world cut off from her, she isolated herself for a time, lost in books and other learning. Determined to make the best of things, she spent countless hours re-learning this world’s magic…or as they called it..Science.
Having a keen mind already, she graduated from accelerated courses in several fields of study. As the media storm of discovering alternate dimensions existed as well as the new powers the raw magic shockwave randomly gave the world died down, Twilight lost touch with most of her friends when she and the rest of the survivors were immigrated to Equestrian City across the bay.
Crippled by the death of Spike from seemingly old age, she slipped into a deep depression, lost in what direction to go now that one of the last connections to her home was gone.
In the meantime, everyone exposed to the blast began exhibiting new and unique powers from mere super speed to flight abilities to invisibility. Some began to use their powers for their own selfish wants and needs, and a superhero level of crime began to rise that conventional justice could not control. As such, the non-meta civil services were fighting a losing battle against these super villains, and needed some sort of edge.
Twilight realized, with a bit of help from her friends, that she shouldn’t dwell on the past, but focus on the future. Teaming up with the now successful Rarity and Silver Spoon, she began working as the head of research and development for their Tech Company Diamond Labs. Given mainly free reign, she went on to begin building prototype power armor for the ECPD.
Using her abilities and resources, Twilight began to construct and perfect a suit of powered armor that reflected both her true form from before she was stranded. Faced with a deadline to deliver the armor, she began testing it herself, taking data from battles and keeping her identity a secret. Taking on the name the Masked Matterhorn, she became a force to be reckoned with on the streets of Equestrian City.