Lightning bolt increase?

[Nifelheim]

In a battle, upper left corner, there a lightning bolt icon. I'm at 6/6. How do you increase this? Some attacks use 7+ to be used.

[kryton]

This is your power ability. It will increase as you level.

[Nifelheim]

Ok thanks. I'm at level 18 so still new, and working on maxing all my 3stsrs to 60