Sure! There's a fanfiction called 'Harmony of Darkness'. In this story, Marceline and Marshall Lee are on a journey to find a lost melody that has the power to change the balance of their world. Their relationship is at the center of the story, and as they search for the melody, they discover new things about each other. Another one is 'Blood and Roses'. This one focuses on their more vampiric natures and how they deal with love and power. It has a great blend of action and romance. And 'Starlight Serenade' is a fanfiction that features them in a celestial - themed adventure, with their feelings for each other growing as they face the challenges of the starry realm.
Well, 'Eternal Bonds' is a Marceline and Marshall Lee fanfiction that's quite interesting. It portrays their bond as something that transcends time and space. It has some really cool plot twists where they have to face challenges together that test their relationship. Then there's 'Frosty Meetings', which is set in a wintry landscape and shows a different side of their dynamic. It's full of cute moments and some deep conversations between them. And don't forget about 'Moonlit Rendezvous', which is all about their secret meetings under the moonlight and the feelings that develop during those times.