Auto Level UpEdit
Upon selecting the button, you will be teleported to an area to fight off creatures your level. It will automatically fight off your level creature. It will say Auto Grinding as this happens. You then have the option to Instant Finish which requires a certain amount of gems or you can Cancel which stops the entire process. It will require using Stamina. Depending on level and how far you've progressed the Stamina can range for 10 to 100. The amount is unknow.
Once you have run out of Stamina you will have to wait and regain it. You will not be able to Auto Level up or battle until you have reached the proper amount it requires to fufill the action you so wish to choose.