Professor Juniper will give it to you after you beat Iris, (exit the gym, then Juniper appears). Also you can get one in Castelia city after you have 50 different Pokemon IDs, which means you have to have traded 50 times or more and it's the guy in the black suit in the Castelia city Pokemon center.You don't have to use your master ball that you get from Professor Juniper on the Reshiram. The game wants you to catch it with any ball, I caught it once with Quick Ball. I don't know if this will work with you but it is worth at try, and always save before and after something important!
the master ball is for zekrom in white and reshiram in black
yes, you can catch ANY pokemon with a master ball, reshiram is who it is aimed at in white 2
with master baLL
you can trade a Pokemon from black or white holding a master ball.
Yes you can I have done it
don't have the game
In white you use the master ball in black you trade
master ball or get power low
Throw a Master Ball at it.
only in Pokemon white by urself if u have master ball!
professor juniper gives it to you
The Professer will give it to you after the last gym