The legendary dog you find the dog that has a type advantage over your starter.
you can use it when ever you want but i recomend using it on mewtwo
Find it on a route in the grass then use the masterball.
the masterball is for any Pokemon you want, it can catch them without fail ( it will ALLWAYS work ) . you are supposed to use it for mewtwo though. :P
It's highly recommended to use it on your legendary dog Pokemon whether it's Raikou, Suicune or Entei.
when you find that Pokemon if you have a master ball with you use a pokeball and you will capture it
on any legendary(just that it should be a strong or rare legendary)
First you have to find it which you can find it pretty much anywhere the best route is Route 1. Use a masterball on it to easily capture.
on the legendary Pokemon that you encounter on the game thx for reading x --:)--x
Choose bulbusaur as your starter receive the national pokedex deliver the ruby and sapphire to celio then look around kanto for it and use your masterball on it.
It isn't meant for any one pokemon. Most people use it on Mewtwo, which you probably should use it on. You can catch the legendary birds and Mewtwo without a Masterball but it can take a long time.
Meytwo, articuno, zapdos or moltres and heres why. meytwo take alot of hard work to get that guy to move unless you use cheats. use MASTERBALL WISELEY
if u use any masterball cheat u get bad egg in Pokemon PC