You can use your Skill Scroll to upgrade a specific Skill that your Hero Card has.
Upgrading willimprove the skill stats or lower the cooldown of the skill.
The color of the required scroll matches the color of the hero. The better the skill, the more rare the scroll you need for the upgrade.
For example, let's say you have a blue Skill Scroll and a Henrich in your Hero Collection.
Henrich's individual skill is the Tsunami, and his Combo Skill (combined with another Hero Card, who must be in the party, or selected from your reinforcement -list before starting a Dungeon) is theWater Transform.
When you select Henrich from your Hero Collection, you can tap on the Skills -tab and spend a Skill Scroll to increase his Tsunami Skill. This will increase the damage caused by the Skill and also reduce its cooldown period (the time it takes for the skill to recharge).
When you upgrade a combo skill remember that both combo heroes have a separate cooldown and both need to be upgraded for the skill to be active after fewer turns in battle.
Leader skills are passive boosts to your party's stats. Some leader skills boost heroes in your party that are the same element or of a certain trait. Some leader skills activate a boost when you draw 21.
Leader skills can't be upgraded with scrolls.