Hero Challenge events allow players to collect a significant amount of Hero Fragments per battle. Each event focus on a particular character and tend to have specific restrictions, such as hero levels, hero ranks or specific heroes. So far there have been three kinds of events: 5 days Hero Challenges, Featured Events and 24h Hero Challenges.
5 days Hero Challenge
Main article: 5 days Hero Challenge
5 days Hero Challenges replaced the 24h Hero Challenges. These challenges run for 5 days and are composed by 12 stages with 3 boss nodes.
Main article: Featured Event
Featured Events, formerly known as 7 days Hero Challenges, started on the 22nd of December 2016 with the Multiverse Collapse event where Supergirl fragments were the reward. These events last for 9 days and it's possible to collect up to 500 hero fragments.
24h Hero Challenge
Main article: 24h Hero Challenge
24h Hero Challenges ran weekly, on Saturdays (GMT). They are composed of 5 battles and each battle carries a reward of 5 hero fragments of a specific hero. On May 2017 this challenge was replaced by the 5 days Hero Challenge.