How do the Avengers cards that came in the bricks of Avengers Assemble work? I have a Nova card, but the only Nova piece I own is the Mutant Mayhem 221 Nova. I have no idea how it works though.

The mechanic is on the card and pretty clear. However if you can't figure it out from the card, here's a video demo-ing it.

https://www.youtube.com/watch?v=4Qzx5ZhDqpk

So far they haven't defined them. Seem kind of like the constructs and can be on teams in addition to resources etc.

It was mainly the 5 squares away and disappear that I don't get. If a character I bring in has 11 Running Shot and I move the 6 squares to take the shot, does he get immediately discarded before the shot is taken because of the 5 square rule or can he take the shot and then be removed? It says "immediately", usually things like that say "after actions resolve".

I would say the instant it's more than 5 squares away, it's removed.

Also, it should be mentioned that MM 221 Nova is the wrong Nova to work with the Nova ID card, if you didn't know.

It says any piece that shares the name Nova or the real name on the back of the card...