Then, come up with an interesting concept for your fanfic. It could be about a team - up between RWBY characters and Hiccup and his friends. Or perhaps a situation where the Grimm from RWBY are attracted to the dragons in HTTYD. Plan out your plot carefully, thinking about the beginning, middle, and end.
First, get to know both universes really well. Study the characters, settings, and rules of RWBY and HTTYD. For example, in RWBY, there are different kingdoms and unique fighting styles, while in HTTYD, there are various types of dragons with distinct behaviors.
Chapter 199, "Good News Keeps Coming for the Hong Gang Family (Part 2)", is the clearest early answer because it turns Hong Gang's situation into a concrete plot event. A useful checkpoint is the way the scene starts with Husband Hong Gang is the captain of the Green Wolf Team of the... and follows through with All children should have no disparity..
Chapter 211, "Elite System, Mining, and Cheng Ping's Grudge", is the clearest early answer because it turns Xia Hong's situation into a concrete plot event. The chapter gives readers a real answer by opening on The two swords on Xia Hong's back were actually quite noticeable. and ending on Do you think I don't dare to kill you?" "I mean no such thing, just....
Chapter 205, "The Director Emerges, Treasure Presentation Opportunity (3)", is the clearest early answer because Treasure Presentation Opportunity gets a payoff that changes the stakes. The chapter gives readers a real answer by opening on Leader, this must be the Great Xia Leader..." Xiang Liang looked at... and ending on Who is this person?" As Yuwen Dao climbed the stairs with the four,....
Chapter 175, "Ape Mountain, Xiao He Camp", is the clearest early answer because it turns Big Sister's situation into a concrete plot event. It opens with On the north shore of the Xing River, the air was filled with a large... and closes on Fortunately, though immature, Xiao Hen has never caused any real....
Chapter 244, "Hunted Down, Strength, and Rescue (Part 3)", is the clearest early answer because it turns Divine Archer's situation into a concrete plot event. The chapter turns that into something concrete by moving from The moment they saw Xia Hong's true face, it was filled with... to However, at that moment, an iron arrow suddenly shot in from outside....
Chapter 210, "Hong Yu, Beehive, Observation", is the clearest early answer because it turns Great Xia's situation into a concrete plot event. The chapter gives readers a real answer by opening on Zifeng returning to the nest." "Coming!" From beneath the boulder,... and ending on Among the ringed wooden houses were three rings of roads leading....
Chapter 309, "Gamblers at the End of the Road, Li Family's Swan Song", is the clearest early answer because it turns Cloud Dragon Army's situation into a concrete plot event. The setup is As Li Xuanling revealed her plan step by step, unlike those Li clan..., but the pressure keeps building through He only just realized why Li Xuanling had previously led everyone....
Chapter 239, "Shifting Situation, Great Xia Special Envoy (Part 4)", is the clearest early answer because it turns Qiu Peng's situation into a concrete plot event. The chapter gives readers a real answer by opening on Is there a young Cold Resistance Level? and ending on I hope the people of Long Mountain are aware of this!" After these....
Chapter 266, "Assessment Objective, Hell Level Difficulty", is the clearest early answer because Cold Beasts finally turns buildup into a real advancement. The chapter turns that into something concrete by moving from So scared before it even starts?" "Teams of a hundred, weapons, bows... to Within the camp's circle of young people, Xiao Hen still held a....
Chapter 191, "Repel the Enemy and Punish, The 1st Wedding", is the clearest early answer because it turns Hive Camp's situation into a concrete plot event. A useful checkpoint is the way the scene starts with From the north, a fierce wind swept in. and follows through with The words "effortless" and "exhausted" were now fully realized in the....