Don't just use your strongest cards. Using a card depletes its usage for that map, and once exhausted, it's gone for the remainder of that mission.
Cards are your most valuable resource, determining your , Power (ATK) , and unique Skills . Yggdra Union
Try to finish maps quickly to earn the MVP bonus , which gives permanent stat boosts to the unit that dealt the most damage. Don't just use your strongest cards
Only Big Stars in a character's stats matter; "Small Stars" are just progress toward the next big one. Use stat-up items when a character is furthest away from their next big star to get the most value. and once exhausted