How do you find out the power cost to use an ability?
Last Updated: 98d
While in battle, tap on the icon representing your hero. Next, tap on the gem color for that ability. The number below the ability name is how many of that color AP it costs to activate the ability.
Outside of gameplay, you can go to the Comic Collection Screen and pick the character you want to check. Scroll the page by clicking the arrow sign to the right until you get to the ability description. The power cost for an ability is displayed there.