Heroes can be promoted to increase their abilities. This is mandatory for any time traveller wishing to restore the timeline!

 

Earning multiple of a Hero card will allow you to promote them using XP. The number of each Hero to collect for next upgrade is shown on the Hero card. In Events, you can use EXP!

 

When you have enough XP and have collected enough of one Hero, you will see blue flame on Hero card. This indicates you can upgrade the Hero (and is also very cool)!

 

Keep in mind, Agent, that the higher promotions a Heroes receives, the more XP you'll need to use to promote them further.