How to find the three missing pokemon (especially Steelix) inpokemonlight platinum

In pokemon light platinum, there was a stage where I got stuck and so I couldn't find 1 of the three missing pokemons (stelix) so I trie...

Challengers Cave - WalkThrough

The question still remains...is there actually a legendary pokemon here? Because I didn't find one.

How to catch and find Terrakion

Fly to the Pokemon League, or once you've defeated the Elite 4 than do so. Head south and then take the first tunnel to your right ( or ...