There are normal and elite Campaigns, and 8 chapters for both types: Kingsdor, Sunsingers, Flamehammer, Steambeards, Anthropos, Moonsekers, Bloodbite and Nightspears, each one with 8 stages for you to fight. First you unlock normal campaign, and when you have finished all 8 stages, you can attempt elite campaigs.
When you finish a stage in an elite campaign, you will get one, two or three stars. Once you’ve achieved 3 stars for a combat, you’ll be able to auto clear it repeatedly, which will give you a series of items and soulstones. Collect 10 Soulstones to summon the corresponding Hero. The Soulstones are also required to upgrade the Hero.
This article received help from the guide written by ooooclaire @ mobileroyale.forum.igg.com