He might try to engage Slade in conversation. Nightwing is smart and could be looking for a way to psychologically get an edge over Slade. He could be probing for Slade's motives, hoping to find a way to turn the situation around. He might also be stalling for time, waiting for the right moment to make his move.
It's also possible that Nightwing and Slade end up having a long conversation during the captivity. Slade might try to convince Nightwing to join his side, perhaps by appealing to some sense of justice that he thinks Nightwing is missing. Nightwing, of course, would resist, but this could lead to some interesting character development for both of them as they debate their different ideologies.
He may also try to talk his way out. Nightwing is known for his charm and intelligence. He could try to reason with Slade, find some common ground, or play on Slade's emotions. Maybe he could remind Slade of a past event where they had a moment of mutual respect, hoping to make Slade let him go.
One possible motive could be revenge. Maybe Nightwing has thwarted Slade's plans in the past, and Slade wants to get back at him. Another could be that Slade sees Nightwing as a valuable asset. He might plan to use Nightwing's skills for his own evil purposes, like forcing him to steal something or gather information for him.
It's not appropriate. Fanfiction should focus on exploring the characters' personalities, relationships in a non - sexualized way. 'Slade and Nightwing' have complex relationships that can be explored through friendship, rivalry, etc., but sexualizing them is not acceptable in the general fan community.
Well, it could mean that in the context of fanfiction, the character Slade is depicted as a protector of Nightwing in the stories created by fans. Maybe in these fanfictions, Slade has a role where he safeguards Nightwing from various threats within the fictional scenarios that the fans have come up with.
One common theme is the struggle between good and evil. Nightwing represents the good side, while Slade often toes the line. Their interactions often revolve around this dichotomy.
Some fanfictions show Slade taunting Nightwing about his relationship with Batman. This can create tension between Nightwing and Batman as Nightwing might feel the need to prove his independence. Batman, in turn, may be overly protective, which Slade can use to his advantage. The interactions can also lead to unexpected alliances. For instance, in some stories, Slade and Nightwing might have to work together briefly against a common enemy, much to Batman's dismay.
In this kind of fanfiction, Robin might be in a lot of danger. Slade could be using Robin to get to Batman. He might try to brainwash Robin and turn him against his friends. For example, he could lock Robin in a secret lair and show him false information about Batman to make Robin question his loyalty.
Nightwing would initially be defiant. He's a highly trained fighter and detective in his own right. So, he won't cower in front of the Joker. He'll probably try to size up the situation, looking for any weaknesses in his captivity and the Joker's plan.