How do you get to blackthorn city from mohagony city?

Answer 1

you have to find lance and red gyaradose, after that, go to the sign next to the old guy and there is man standing in front of him. Go to him and he will tell you to go and intercept a radio signal from team rocket. Go to the house next to the pkmn center and he will be there follow the path and follow what he says and beat it. Next, elm will call to go to goldenrod city. beat team rocket and blah blah there. you will be given the rainbow wing or the silver wing. (Gold or silver) Next go to either the cave near cianwood or tin tower in euratik city. (Ho-oh or Lugia) then you go to mahogany town and you will be able to go to black thorn city. (You need to pass a cave though)

Answer 2

You go down Route 45 and then Route 46 to New Bark Town. You have to go through the routes twice to beat all the trainers. If you don't bother just fly home. Talk to Professor Elm and he'll give you a Master Ball. Now fly to Ecruteak and save before the Dance Theater. When you enter the theater, the Kimono girls will challenge you they have:

All lvl.38: Umbreon, Espeon, Flareon, Jolteon, Vaporeon. They're hard to beat so stock up.

Then they will head off to Bell Tower(HG) or Whirl Islands(SS).

Just get through the place and Ho-oh/Lugia will appear.

After you have battled them you can go through Route 27 and 26 to get to the Indigo League.

Hope that helps.