They could become friends. Draco, having been saved by Harry, might feel indebted to him. He could start to join Harry and his friends in some activities, slowly integrating into their group. Harry, in turn, would welcome Draco as he always believed in giving people second chances. They could then support each other in their studies and adventures at Hogwarts.
Well, perhaps Harry uses his quick thinking and his knowledge of magical creatures. He might step in just in time, using a spell to distract Buckbeak before it can harm Draco. For example, he could use a simple levitation spell to lift a small object and draw Buckbeak's attention away from Draco.
In this fanfiction, Harry might also save Draco by appealing to Lucius' sense of self - preservation or family. He could threaten to expose some of Lucius' secrets or illegal activities if he doesn't let Draco go. Or, if there is some underlying family drama involved, Harry could use that to his advantage. For instance, if there's a feud within the Malfoy family that Harry is aware of, he could manipulate the situation in a way that makes Lucius back off and leave Draco unharmed.
It could be some water - dwelling dark creatures. Maybe mermaids with a malicious streak or some sort of lake - bound demons that were awakened when Hermione got too close. They might see her as an intruder and want to harm her, which is why Harry has to save her.
Well, Harry might save Daphne from Draco because Harry is always the hero type. He doesn't like Draco's pure - blood supremacist attitude. Daphne could be a target of Draco's cruel remarks or actions just because she might not fully conform to Draco's ideas. Harry, being the defender of the underdog in many cases, steps in. Also, it could be that the plot of the fanfiction is building a new alliance or relationship web, and Harry saving Daphne is a key part of that, leading to new story developments.
It could be part of a plot where Draco is given an assignment by someone in the wizarding world to save Harry from the Dursleys. He initially does it for self - serving reasons like getting in good with certain powerful wizards who are concerned about Harry's well - being. But during the process, he actually starts to care about Harry.
One common theme is redemption. Harry saving Draco can be seen as Draco getting a second chance, especially if he was in a situation related to his past wrongdoings. It gives him a chance to change.
One possible plot could be that Harry discovers some new evidence that proves Draco's innocence. Maybe there was a frame - up by some dark forces within the wizarding world. Harry, being the hero he is, feels compelled to act and uses his influence and skills to break Draco out of Azkaban. This could lead to them having to go on the run together, hiding from the authorities while they try to expose the real culprits.
It could be that Draco is following orders from some dark forces. They see Ginny as a way to get to Harry, and Draco, being their follower, tries to target Ginny. He might think that by getting Ginny, he can gain more power or favor within those dark circles.
It might start with Daphne being in a vulnerable situation where Draco is about to cause her some harm, like maybe Draco is cornering her in a corridor at Hogwarts and making mean comments. Then Harry just happens to come along and decides to step in.