In pokemon black are there any hidden battles in black city?

Question

In Black City the old man at the back of the largest building says have 10 battles in Black City and he will help you, but there are only a total of 7 trainers. Where are the other 3 trainers?

Answer 1

They are probably at White Forest, which is in Pokemon White. To get those 3 trainers You gotta get a friend with pokemon white and connect to each other using Entralink. Then you have to go to White Forest in there world and talk to people, then i think they ask you to take them to Black City.