In the battles, there are 3 stars:
1. 1/3 time to finish the battle
2. No daemon dies
3. Use skill to finish the battle.
When you finish the 3 all together, you will get a 3-star rating, and you will get more soulstones
For 1: Please improve your daemons as much as possible to increase their str.
For 2: In some challenging battles, please arrange the melee and ranged, and please take healers if necessary.
For 3: When the battle is about to finish, choose a skill you want to trigger, then long press, then when the time comes, release the skill. You will find it much easier to get a final hit by skills.