Skills
Skills can be learned when the hero levels up or by reading a
(sword),
(bow), 
(staff) Skill Book. Skills are automatically available for use in battle when you equip a weapon.
Obtaining Skill
You will automatically learn skills for each weapon type (sword, staff, bow) when reaching Level 5, 10, 20, 30, 40 and 50. For level 50 above, you need to get the Skill Book from Floating Island's Bosses, or buy from other players. The current highest level Skillbooks can be obtained from Zardogan (Underworld 1 Boss).
Upgrading Skill
It is possible to improve a skill using Skill Books (can be obtained from enemy drops and Rift). Depending on the current level of your skill, you will need to use a different Skill Book:
Level 1 to Level 10: 
Lesser Skill Book
Level 11 to Level 20: 
Superior Skill Book
Level 21 to Level 30: 
Greater Skill Book
Level 31 to Level 60: 
Ancient Skill Book
To enhance, follow these steps:
1. Access the Hero menu
2. In the "Skills" tab, select the skill that will be improved
3. Select the "Modify" option
4. Check the amount of Gold and Skill Books needed.
Recycling Skill
Skills that have been improved can be recycled. Recycling a skill consists of recovering part (or all) of items used to improve it.
To recycle, follow these steps:
1. Access the Hero menu
2. In the "Skills" tab, select the skill that will be recycled
3. Tap the button 
4. Check the quantity of items that will be received and confirm.
You can use Diamonds or 
Skill Recycle Scroll to recover 100% of the items used to improve the skill.
You can also rearrange your skill according to your needs!
Here are the charts for leveling up skills