How to get lucario in d/p
First of all lucario is not a legendary pokemon.Once you get six badges board the boat to go to steel island. Then (i don't know where but) find a guy in a blue hat that looks like the guy in Lucario and the mystery of mew. After talking he will join you and have a lvl 34 lucario.All you have to do to get lucario's pre-evolution is to go deeper into the cave and fight people along the way. Then have atmost 5 pokemon with you and the empty space would be the pre evolution of lucario.