Well, Reddit can be a great place too. There are subreddits dedicated to Star Wars fanfiction where people might recommend Cal Kestis and Merrin fanfics. You can post a request asking for good ones, and the community will likely respond with some great suggestions. Additionally, Tumblr sometimes has fanfic writers sharing their works or reblogging others' stories about these two characters.
The 'hurt/comfort' trope is quite common too. Maybe Cal gets injured during a battle, and Merrin has to take care of him, which deepens their relationship. Also, the 'soulmate' trope can be found in some fanfics, suggesting that they are meant to be together on a deeper, almost spiritual level, which ties in well with the Star Wars universe's themes of destiny and the Force.
A lot of fanfics also explore the idea of them facing challenges together, whether it's against the Empire or some other dark force. Their different powers and abilities often play a role in these stories, like Cal's connection to the Force and Merrin's Nightsister magic.
Often their relationship is portrayed as a deep and growing bond. They start as comrades and gradually develop feelings for each other. Their different abilities, Cal's Jedi training and Merrin's Nightsister magic, bring them together as they face challenges.
You can start by looking on fanfic platforms like Archive of Our Own (AO3). It has a large collection of Star Wars fanfics, including those featuring Cal Kestis and Merrin. Just search for their names in the search bar, and you'll be presented with a variety of stories with different themes and ratings.
A really interesting fanfiction is the one where Cal and Merrin find themselves in a situation where they have to protect a group of refugees. This story shows their selfless nature. Cal uses his lightsaber skills and Merrin her unique powers to fend off the attackers. It's a great exploration of their relationship as they work side by side to achieve a common goal.
Fanfiction.net is also a good place to search. Just use the search function and type in 'Cal and Merrin' to see what comes up. However, be aware that the quality may vary on this site.
Maybe a fanfic where Cal and Merrin are separated due to some external force. Each of them has to fight their own battles, but they are constantly thinking about each other. Eventually, they find their way back and realize how much they mean to one another.
Well, it could be the unique dynamic between Cal and Merrin. Their personalities might interact in ways that are exciting to explore in fanfic. Maybe Cal's determination combined with Merrin's mysterious nature creates interesting storylines.