Crossover

Give your characters a concrete reason to be together. Don't just drop them in; use shared mechanics (like similar magic systems) to make the meeting feel organic.

If one universe has significantly stronger characters than the other, you'll need to find a way to balance them so one doesn't completely overshadow the other. Crossover

The crossover is a fundamental move used to change direction and beat a defender. The Between-the-Legs Crossover | Basketball Give your characters a concrete reason to be together

If posting online (like on AO3 or Reddit), always tag your story clearly as a crossover so the right fans can find it. 🏀 Basketball: Mastering the Dribble Crossover