User blog comment:Leyrann/Riven Rework - Yes she may be able to use one/@comment-25970203-20150126233841/@comment-4834593-20150127065255

You can see the Ki resource the following way: You gain Ki from using abilities and hitting champions, you lose Ki when you're not fighting champions. Just like I believe exact Gnar numbers aren't shown anywhere and yet people can play with it.