The fanfiction could revolve around Twilight's boyfriend being a reformed villain. He used to be on the wrong side but has seen the error of his ways. Twilight, with her kind heart, believes in his change. They start a relationship, and he helps her understand the minds of those who have strayed from the right path. This relationship could be a journey of redemption for him and a learning experience for Twilight about forgiveness and second chances.
Maybe her boyfriend is an ordinary pony at first glance but has a hidden talent for understanding complex magical artifacts. Twilight discovers this when they both stumble upon an ancient relic. They start to work together to unlock its secrets, and in the process, their relationship blossoms. They might face some opposition from other ponies who think Twilight should focus solely on her studies, but they prove that love and learning can go hand in hand.
It could be a new character entirely. A mysterious pony who just arrives in Ponyville and catches Twilight's eye with his unique charm and different way of looking at magic.
One possible storyline could be that Twilight Sparkle gives birth to a magical foal with unique powers. Maybe the foal inherits Twilight's love for knowledge and has an instant connection to the magic of Equestria. The story could then focus on Twilight raising the foal and teaching it about friendship and magic.
A likely candidate could be Discord. He is known for causing chaos and mischief. He might pretend to befriend Twilight Sparkle only to betray her at a crucial moment. Another possibility is Trixie. Trixie has been jealous of Twilight in the past and could betray her out of envy.
The story could revolve around how Jasper and his partner (could be a vampire or a human turned vampire) raise their son. Their son might struggle with his identity, being part of a vampire family but also having a connection to the human world. For example, he could befriend some humans without them knowing his true nature, leading to some tense and interesting situations.
Flash Sentry could be a likely groom. He has shown an interest in Twilight in the past and they have had some interactions that could lead to a romantic relationship. Another option could be a completely new character, perhaps a powerful wizard or a prince from a far - off land who Twilight meets during one of her adventures and falls in love with.
The sword could be a magical artifact she discovers during one of her adventures in the Everfree Forest. Maybe it was left there by an ancient unicorn or alicorn for a worthy magic user to find.
Well, it could represent her connection to a secret society within the fanfiction world. Maybe it's a mark that shows she has a special power or role.
Losing a friendship could make her cry. For example, if Rainbow Dash suddenly stopped being friends with her because of a silly argument, Twilight would be heartbroken and cry. She values her friendships highly.
She could marry Spike. They have a very special bond throughout the series. Spike has always been there for Twilight, and in fanfiction, this could develop into a romantic relationship leading to marriage. They already have a deep connection, and Spike's loyalty and Twilight's intelligence could make for a great couple.
It could be a pony who is extremely extroverted if Twilight is introverted. Someone who loves chaos and spontaneity instead of Twilight's love for order and planning.