One challenge is getting the characterizations right. The Runaways have a very distinct group dynamic, and Cloak & Dagger have their own relationship and personalities. If not done well, it can seem like the characters are just out of place. For example, Gert's scientific mind and her relationship with Old Lace need to be accurately portrayed along with Cloak's brooding nature.
One great 'Runaways and Cloak & Dagger' crossover fanfiction is 'The Meeting of Two Worlds' on FanFiction.net. It has an interesting plot where the two groups accidentally cross paths during a magical event in New York. The characters' interactions are well - written, especially Nico and Tandy's, as they both have powers related to the dark and light aspects.
A cool Cloak and Dagger crossover fanfiction idea could be with Daredevil. Matt Murdock's skills as a lawyer and a vigilante could intersect with Cloak and Dagger's fight against crime. They might start out on opposite sides of a case, but then realize they are after the same bad guys. Another could be a crossover with the Punisher. Frank Castle's no - holds - barred approach to justice could clash or complement Cloak and Dagger's more nuanced view. It would be interesting to see how they interact when dealing with a crime syndicate. Also, a crossover with Jessica Jones could be great. Jessica's jaded detective work and Cloak and Dagger's idealistic heroics could create an interesting dynamic as they all try to solve a mystery in Hell's Kitchen.
First, you need to choose the other universe or character you want to crossover with. If it's, say, the Black Panther, research both Cloak and Dagger and Black Panther. Know their powers, personalities, and backstories. Then, come up with a basic plot. It could be as simple as Cloak and Dagger accidentally ending up in Wakanda and getting involved in a local conflict there. Next, think about how the characters will interact. Will they be friends? Foes? Somewhere in between? Start writing an opening scene that grabs the reader's attention, like Cloak and Dagger in the middle of a fight when suddenly they are transported to a new and strange place.
Overall, Cloak and Dagger stays somewhat true to the comics. Some characters and plotlines are adapted, while others are changed for better storytelling in the TV format. There are additions and omissions, but the core essence remains.
The fate of Cloak or Dagger varies across different comic runs. Sometimes they survive intense situations, while in others, their storylines might take a tragic turn and result in their deaths.