ER 8ER 6Er 7ER 5 Sparks Sparks

Periodically Mighty Party runs events where you can win a currency that is unique to that event. Their image can resemble eggs, coins, and other things that relate to the holiday or topic the event is themed upon.
What are they good for?
While this can vary depending on the event, typically they are used to purchase/open chests that offer Hero Souls (the things you win to get new heroes or level up existing heroes) that can only be obtained (at least at first) by participating in that event. Sometimes the chests award other prizes such as more of the event currency. The more expensive chests offer prizes of increasing rarity. Also usually there is a prize for gaining and spending a certain amount of the event resource.
Where do you get them?
As you might expect, you win it by participating in events and accomplishing the various challenges in it. As with most other game resources, you can occasionally win them in Brawl as well.
Community content is available under CC-BY-SA unless otherwise noted.