Say you start a beam attack that targets Dormammu and others.
You attack Dormammu first and then are pushed by his reaction power.
What happens with the rest of your beam attack?
Does it proceed from the area you were pushed from?
Does it get re-evaluated from your new position (and if so, can you now make an attack against characters who were not part of the original beam)?
What if you can still target some of the original characters from your new position, do you get to continue with your series of attacks?