Heroes come in various rarities, from 1-star to 5-star. While 5-star heroes are generally stronger due to higher base stats and pre-learned skills, lower rarity heroes can be promoted to 5-star using Hero Feathers and Badges. Promoting a hero significantly boosts their stats and allows them to learn more powerful skills. Merging duplicate heroes of the same rarity also increases their stats and raises their 'merge level', making them even stronger. Prioritize promoting and merging your favorite and most effective units.
