Writing a Claggor x reader fanfic can be such a blast, especially if you're just starting out! First, I'd say immerse yourself in Claggor's character—rewatch his scenes in 'Arcane', jot down his speech patterns, and think about how his quiet but loyal personality would interact with a reader-insert. Since he's more reserved, the dynamic could be super sweet—maybe the reader is the one who slowly draws him out of his shell.
For pacing, I’d avoid rushing the relationship. Build tension through small moments—him fixing the reader’s gadgets, sharing a meal in the Undercity, or protecting them during a fight. Use second person ('you') to make it immersive, and sprinkle in sensory details (the smell of oil, the hum of machinery) to ground the story. Bonus tip: Throw in Piltover’s class divide as conflict—maybe the reader’s from the upper city, and Claggor’s wary at first. Honestly, just have fun with it; fanfic’s all about exploring what-ifs!