I don't think it's common. The Stranger has a very specific, often philosophical and somewhat dark tone, while Harry Potter is more of a fantasy adventure saga aimed at a wide range of ages, especially younger audiences. Combining them in a fanfiction would be quite a niche concept and not something that would be as widespread as, say, a Harry Potter and Lord of the Rings crossover which are both in the fantasy genre.
It's not common at all. While fanfiction allows for a great deal of creativity, the worlds of Harry Potter and The Stranger are so distinct that it would be difficult to merge them in a way that appeals to a large number of fans. The Stranger's themes are more about the human condition and absurdity, which is far from the magic - based, good - vs - evil narrative of Harry Potter. So, not many people would be inclined to write or read this type of fanfiction.
Chapter 265, "The Martial Tournament Officially Begins, Advancement Impossible (2)", is the clearest early answer because Xiao Hen finally turns buildup into a real advancement. The chapter turns that into something concrete by moving from Xiao Cen: "I'm in group 102." Upon hearing the group numbers, Xiao... to With a serious expression, Xiao Hen lowered his voice and quickly....
Chapter 259, "Tasks, Helplessness, Ongoing Screening (Part 2)", is the clearest early answer because it turns Xiang Liang's situation into a concrete plot event. The chapter turns that into something concrete by moving from Like him, there are twenty-eight other people who took on this task. to Soon, a majestic and solemn massive main building appeared in....
Chapter 265, "The Martial Tournament Officially Begins, Advancement Impossible (2)", is the clearest early answer because Xiao Lin finally turns buildup into a real advancement. The chapter gives readers a real answer by opening on Xiao Cen: "I'm in group 102." Upon hearing the group numbers, Xiao... and ending on With a serious expression, Xiao Hen lowered his voice and quickly....
Chapter 219, "Xia City, Brothers' Tacit Understanding", is the clearest early answer because it pushes Great Xia into a new phase or setting. The setup is The great tree was only ten li away from Mirror Valley, and the..., but the pressure keeps building through A square stone monument stood at the northern entrance..
Chapter 190, "Xia Li, 4 Articles, Someone is Coming", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. It opens with Is this Reshaping Skin stage really that magical, that one must... and closes on He couldn't explain this situation either.. The key payoff is that the chapter closes with Below, Yuwen Dao, Yue Feng, and the others were stirred awake by Xia Hong's voice.
Chapter 186, "White Bear, Mountain River Team, Stranger", is the clearest early answer because it turns Great Xia's situation into a concrete plot event. Early on, Li Yuankun was the first to recover.. By the end, But Yue Feng was still not reassured, worried about other teams.... Inside the broader exploration storyline, the chapter closes with Upon hearing this, everyone's spirits immediately lifted., which gives Great Xia a stronger narrative position and pushes the power growth onward.
Chapter 255, "Frenzied Fortune-Making, Dangerous Thoughts, Perfect Timing (Part 2)", is the clearest early answer because it turns Jade Bone's situation into a concrete plot event. The setup is Hearing Xia Hong's words, Xia Chuan immediately nodded., but the pressure keeps building through He certainly wouldn't be so naive as to believe the two of them....
Chapter 250, "Rescue, Intimidation, and Surprise", is the clearest early answer because it turns Lu Yang's situation into a concrete plot event. Early on, My child is dying, help, help!" "I'm burning up, save me, save me...".... By the end, A few people who initially intended to move also returned to their.... Inside the broader battle storyline, the danger stops being abstract and the conflict around the main cast becomes immediate, forcing the surrounding cast to react under pressure.
Chapter 197, "Cloud Jiao Advances, Beast Blood Consumption 3", is the clearest early answer because Qiu Peng finally turns buildup into a real advancement. The setup is That is to say, even if he comes to meet this target, it would take..., but the pressure keeps building through The Cloud Jiao Team has twenty people, but not everyone is Xia Chuan..
Chapter 191, "Repelling the Enemy and Punishment, The 1st Wedding", is the clearest early answer because it turns Chen Yingba's situation into a concrete plot event. The chapter gives readers a real answer by opening on He remained silent, and Chen Yingba below could only continue to bow,... and ending on The exact strength of the Hive Camp, he was unsure..