You must catch a sandile or krokorok and level it up. Visit the pages for each pokemon http://pokemondb.net/pokedex/sandile & http://pokemondb.net/pokedex/krokorok respectfully
You can catch a Sandile (on Route 4 or Relic Castle) or a Krokorok in Relic Castle
In preference catch a Sandile in the level 22 or a Krokorok in level 50 (It will evolve in 51)
