I just skimmed your other “thinking about returning” thread, and it seems that nobody mentioned the alliance-locked boss battles. Here’s the rundown:
There are two so far: Avengers vs. Ultron and Galactus Hungers. (I’ll dine on a tasty meal of corvidae if there isn’t one for En Sabah Nur next summer.) When you join the event, your points all go to the alliance you are part of right at that minute. If you leave your current alliance, your points still go to the alliance you were part of when you joined.
These each have 8 rounds. During a round, all the members of the alliance work at scoring points to reach a particular threshold, which increases from round to round. Most of the points scored come from fighting the boss, whose level, health, and damage increase from round to round. Once you defeat the boss once, you’re locked out from fighting him for 8 hours - unless you attempt one of the side battles.
There are 5 side battles at a time. Usually, one character is required for two of those, and a different character is required for each of the remaining 3. All four characters will be chosen from the list of boosted heroes for the event, which is generally larger than for a normal event and includes heroes at every tier. Beating a side battle unlocks the boss again, but keeps that pin locked afterward. All the side pins reset every 8 hours, and I think I remember that the boss unlocks at those same time intervals. The essential characters per node definitely scramble then, too. For the four runs we’ve had so far, if a character has multiple versions - e.g., Captain America - you can use any version of that hero for a required pin.
I’m in Central (Chicago) time - for me, the event will start at 11 AM. The major reset times are therefore 11 AM, 7 PM, and 3 AM.
All along the way, there are variations of personal and alliance progression rewards. There are frequently some decent chances at acquiring Hero Points and big ISO chunks along the way. The last run was before the introduction of Command Points, but I anticipate seeing them as possible rewards the next time one of these is run.
I think that’s a pretty thorough overview, but let me know if you’ve got any questions. I know I think they’re a blast when they happen, and I’m kind of hoping something like that is the holiday event, or running simultaneously with it. (Do you know about the Gauntlet, I think?)