Skills are the backbone of the heroes. These abilities boost the stats of the heroes and their units. A hero with skills is much better off than one without them.
Skills are broken into quality and numerical values. These represent what skill books can be taught to what hero and their value.
What heroes can learn what tomes?
White and Green heroes can learn up to Green level tomes or Skill Tome II's.
Blue Heroes can learn up to Blue level tomes or Skill Tome III's.
Purple Heroes can learn up to Purple level tomes or Skill Tome IV's.
Orange and Red Heroes can learn up to Orange level tomes or Skill Tome V's.
Does a hero's specialization effect what books they can learn?
Yes, dependent on the heroes Specialization depends on what skills they can learn above Skill Tome II quality.
Help! I just started and one of my heroes has two skills, but they aren't the right type?
Yes this is a known issue to help your starter hero gain a little bit more power. As it is a balance type there are only two basic skills that go with it, healer and acclaim. They have 4 slots on a blue hero thus can learn those last two if you feel like opening up the last two slots. The skills will be decent on the hero though till you find another hero to replace him with. He is your starter hero after all.
Learning the skills
The skills learning is achieved by learning from mainland skill master, select the heroes and the skills you want to learn.
Ways to get Hero skill slots
The hero skills have two spare skill slots, four closed at most. The higher quality the hero is, the larger amount the skill slot could be open.
To open the skill slot, you should talk to the mainland skill master, select the unopened skill slot, then click on "Add a Skill Slot". This will pop up a confirmation window where it will cost you 10g to open the slot.
To upgrade the skills
After learning the skills, you need to learn more advanced skills to upgrade them, when upgraded; they will replace the former basic skills to finish the upgrading. The upgrading ways are the same to the skills learning, select the relevant skills, confirm and the next rank replace the former one.