The skeptic in me is worried, but I will reserve judgment until we see how it goes. I am glad to see them trying something new and a bit more creative even if it does sounds awfully complicated.
I understand your confusion! As I have a mild form of dyslexia, I had to watch the live stream at least five times to figure out what they were talking about. So I'm going to put out my take on how it works, after watching the video so many times and hopefully this will help someone else.
There are 2 ways to earn EC:
1 - Maleficent has cursed the building, tap the buildings to remove the curse and you will gain EC. Once the curse is lifted, you can then collect the magic said building provides.
2 - Challenges: Our job is to send the characters off in groups to battle Maleficent and the curse. When you send them off and they finish said battle you collect EC.
The Battles (they call it challenges):
Based on the video you can send up to 4 characters to battle Maleficent and it APPEARS that the battles will be 2 hours. Once the battle has been completed the characters will need to REST and you WILL NOT BE ABLE TO USE THEM AGAIN - UNLESS......
Option A - you help them recover by feeding them, what looks like hot cocoa and marshmallow. You are given 2 for free. You can gain more recovery treats based on tasks in the game (like when we collect token for characters it seems)
Option B - there is a REFRESH button and that can be pressed ONCE per DAY (my own opinion - PAY ATTENTION to the TIME if you're doing to do a big group refresh so you know when it'll be available again - just my opinion)
Option C - There is a feature character and character group (they didn't discuss the group aspect) The feature CHARACTER DOES NOT REQUIRE a REST period. Which means if you happen to run out of characters to send off, you can still send off the feature character to get points and EC. They mentioned that the higher level up the characters are, the more POINTS and EC you can gain.
Each battle will also get you POINTS as well as EC. The points are for bonus rewards along the way and the system works very much like the mini events we've seen in the past X-amount of Points will get you a prize and it appears that each prize for the chapter 1 quests are all EC so that's good for us.
It appears that the point of this entire thing is to get Jack Jack from the Incredibles and we are "buying" his tokens with EC. (I like this option. work hard, get the EC, get the tokens, get the character - again just my opinion).
I hope this clarifies some things for anyone like me who found it confusing and had to watch it several times over to get it. I really am excited about this event. I hope I'm not proven wrong.