filling you're national pokedex
in spear pillar. Oh,by the way its called dialga not diamond you will have to fight some people first.
cant fight just capture
use a rock type pokemon.
beat the Pokemon league
er...fight it with your Pokemon and then throw a pokeball at it. it should catch it... yes fight it but not kill it
in fight area
A fight type
nop
At the fight area (after you beat the Pokemon league)
You have to go to Veilstone City and fight the gym leader there first.
Get your pokedex completed, and get tyhe national dex.
A gastradon in the pokemon diamond, is a pokemon. He can evolve into different pokemons' and also fight other pokemon. He eats leaves, vegetables, and fruits.