Rage of Thunder
Rage of Thunder is a skill that you can use from level 1. The higher the skill, the higher the damage. The skill can be learned, as the level increases, up to level 10. The books are all available at quest rewards, but if you "lose" one, you can buy it at the grocery store for some silver.
Rage of Thunder only works if you have Firewind Stones in your inventory. For every use of this skill, one Firewind stone is consumed. You can get some of them in quests until level 50, after that they are available in the event token shop.
The skill Fire Whirl works like Rage of Thunder and also uses Fire Windsteps. It has a higher range than Rage of Thunder. But unfortunately the Fire Whirl skill can only be used in the training course.