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.
In this fanfiction, an ancient and powerful pony from Equestria's past could betray Twilight Sparkle. This pony could have been awakened from a long slumber and, seeing Twilight as a threat to their old - fashioned ways or power, decides to betray her. Additionally, a pony from a different land that Twilight tries to help might betray her. She might offer her knowledge and resources to this pony, but instead of being grateful, the pony betrays her to get more power or to take over Equestria.
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.
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.
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.
One example could be a fanfiction where Twilight Sparkle is betrayed by a close friend in Canterlot. Maybe her friend reveals her secrets to the wrong ponies, causing chaos in Twilight's life. Another could involve Twilight being betrayed in a magical competition by a fellow unicorn who cheats and blames Twilight for it.
It could be Discord. He loves causing chaos and kidnapping Twilight Sparkle would be a great way to disrupt the harmony in Equestria. He might do it just for fun or to see how Twilight's friends would react.
It could be Discord. He loves causing chaos and might capture Twilight Sparkle just for the fun of it or to disrupt the harmony in Equestria.
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.
Well, in this type of fanfiction, it might be that Twilight Sparkle is betrayed by a mentor figure. This mentor could have been teaching her false information all along, causing her to make mistakes that put her and her friends in danger. Or it could be that she is betrayed in a love - related situation. For example, if she has feelings for a certain pony and that pony pretends to reciprocate only to use her for something else, like getting access to the library in Canterlot. There are so many directions this fanfiction could take.
There could be some jealous ponies in Ponyville as antagonists. They might not understand Twilight's relationship with the changeling and start spreading rumors. This could create problems for the couple, like making Twilight doubt the changeling or making the changeling feel unwelcome in Ponyville.
They often interact as teacher and student. Luna, with her vast knowledge of the old magic, can teach Twilight things that are not found in modern magic books. For example, Luna might show Twilight how to communicate with the spirits of the night.