One idea could be an adventure where Elsa teams up with a dragon (to tie in with the dragon master idea). Maybe the dragon is from a far - off land and Elsa has to learn to communicate with it to save Arendelle from a new threat.
One idea could be that Elsa is a powerful sorceress from a far - off land who arrives in Westeros during the War of the Five Kings. She could use her ice powers to control the weather and influence battles. For example, she might freeze the moats of castles to make them easier to invade or create ice bridges over rivers.
You can try fanfiction websites like Archive of Our Own (AO3). There are tons of fan-written stories there, and you're likely to find some great Elsa fanfics. Just use the search function and type in 'Elsa' to start exploring.
A possible plot could be that there is a lemon - themed festival in Arendelle. Hans, who has returned after his banishment, tries to win Elsa's forgiveness during this festival. Elsa is initially skeptical but as they both participate in the lemon - inspired games and activities, they start to develop a new relationship that is different from their previous encounter.
One plot idea could be that Anna discovers a new magical power within herself and Elsa helps her learn to control it. This could involve a journey through the Enchanted Forest where they face various challenges together and their bond grows stronger as a result. Another idea is a time - travel plot where they go back in time to prevent a past event that had a negative impact on their relationship. They could also face a new villain who is specifically targeting their sisterly bond, forcing them to work together to defeat the foe.
One idea could be that the OC is a powerful mage from a far - off land who comes to Arendelle during a time of new danger. The OC meets Elsa and they initially have a bit of a clash due to their different ways of using magic. But as they face the new threat together, they start to understand and respect each other more. Eventually, they combine their magical powers to save Arendelle and in the process, form a deep friendship or even more.
One idea could be that they are on a quest together in a magical world. They have to overcome various obstacles and their relationship grows stronger as they rely on each other's skills.
Well, a possible plot is that Elsa's pregnancy is a result of some magical encounter. As she progresses through the pregnancy, she starts to notice that her unborn child has an affinity for ice magic even before birth. She then decides to create a special, safe place made of ice for the baby to be born in. And also, she could have dreams about the future of her child, which guide her in making decisions for Arendelle's future as well.
A possible plot is that Elsa's kingdom is threatened by a force that is related to the same kind of threats the Avengers face. The Avengers hear about her and her powers and travel to her world to offer their help. Along the way, they learn about her backstory, and she learns about their heroics. Together, they combine their powers to save her kingdom and in the process, Elsa decides to join the Avengers on some of their adventures in their own universe.
A plot idea might be that there is a strange blizzard that is not caused by Elsa. Kristoff, suspecting foul play, comes to Elsa for help. Together, they discover a dark sorcerer is behind it. As they battle the sorcerer, Kristoff helps Elsa see that she doesn't have to be afraid of her powers and can use them more freely. This could lead to a deeper friendship or more between them.
Well, perhaps there could be a fanfiction where Hiccup and Elsa are both summoned by a powerful wizard to help with a prophecy. They don't trust each other at first, but as they face the challenges set by the wizard, which include tasks that require both fire (from Hiccup's dragon) and ice (Elsa's power), they start to respect and care for each other.