CAMPAIGN STAR CHALLENGE
Completing Levels in the Campaign can earn you Challenge Stars, which unlock a huge series of rewards to help you summon new Invokers, Titans, and progress quickly.
Each Campaign Difficulty has its own set of Star Challenges – the same requirements, but increased difficulty and increased rewards.
As you earn Stars, you unlock rewards – simple.
You can earn up to 5 Stars on each Level in every Chapter – a total of 50 Stars per Chapter.
You can see your progress for each difficulty on the Star Tracker at the bottom of the Map.
Tip: Hit the ? icon on the tracker to open up the Challenge Completion Requirements and the full Reward list.

COMPLETION REQUIREMENTS
To earn a Star, you'll need to beat a Level while meeting certain requirements.
ALL ALIVE: Beat the Level with all four Invokers alive
ALL CHESTS: Beat the Level with all four Invokers alive, while opening all the Chests on the Level
On Auto, your team will not actively seek out hidden Chests – do this on Manual.
SINGLE ELEMENT: Beat the Level with all four Invokers alive, using Invokers from a single indicated Element
Each Chapter (and therefore Level) will specify which Element you need to use.
For example, for Chapter 1, this is Fire.
SINGLE FACTION: Beat the Level with all four Invokers alive, using Invokers from a single indicated Faction
Each Chapter will also have a dedicated Faction that you need to use.
For example, for Chapter, this is the Eldrin Faction.
SOLO: Beat the Level with only one Invoker
For all of the Challenges except Solo, you must:
Use a full team of four Invokers (Titans don't matter)
Have all of your Invokers alive at the end of the Battle. They can die and be revived during the battle, but they have to be alive when you finish the Level.
This means that even if you take a single, super-powerful Invoker from the right Faction and right Element, then beat the Level and find all the Chests, you won't earn every Challenge Star in one shot.
LEVEL CHALLENGES
To see which specific Elements and Factions you need to use to complete each Level, just hit the “Challenges” tab on the Level Select screen:

REWARDS
You can only claim each Challenge Reward once.
As soon as you earn them, you can claim them immediately from either the Map directly or the Rewards tab (accessed after hitting the ? on the Map).
The rewards are focused around helping to grow your Collection and improve your Invokers and Titans.
Campaign Challenges are one of the biggest sources of:
Stars to summon new Invokers
Orbs to summon new Titans
Codexes to upgrade Invokers’ Skills
Prisms to upgrade Titans’ Skills
Echoes, Gold, XP – and everything else you need to upgrade your team.