there are several ways to do this.
1) u can damage it down to low red health and then put it to sleep or paralyze it and then throw an ultra ball or, depending on how long the battle has been going, a timer ball. then, when it starts wiggling in its pokeball, press "A" every time it wiggles to a side.
2) u can use the masterball u get in-game.
3) u can use a GameShark or an action replay to hack masterballs into your game.
4) u can use a gameshark or action replay to hack in a cheat that lets u always catch a Pokemon even in a pokeball.
It is a rare pokemon, but it is not a legendary pokemon
Unknown is not a legendary Pokemon but it is considered rare. Legendary Pokemon are one of a kinds.
no lileep is not a legendary pokemon but it is an ancient pokemon
The legendary is palkia
Noivern is not a Legendary Pokemon.
Is sawk a legendary pokemon??
No, Blastoise is not a legendary pokemon.
No, snover is not a Legendary Pokemon
Azelf is a legendary Pokemon.
Groudon, Kyogre, and Rayquaza. Groudon is the fire legendary pokemon, Kyogre is the water legendary pokemon, and Rayquaza is the air legendary pokemon.
Arcanine is not a legendary Pokemon because legendary Pokemon can't be breeded and arcanine can.