Lucario are renowned for their remarkable speed and agility, and their weight is not significantly higher than most bipeds of their height made of skin and bone. Despite this, they are one of the imprecisely named "steel" type, their spikes and skeleton made of a remarkably light yet sturdy metal once used in the swords and armor of great soldiers and legendary heroes: mithril.
The mithril mines were exhausted in a more heroic era, so for the past few centuries, unscrupulous individuals have sought to "mine" mithril by killing and selling Lucario. Although gunpowder has largely ended mithril's military use, it still shines more brightly than gold, and commands a higher price for sale. But these poachers are all but inevitably stymied, for Lucario are swift runners who can see a hostile aura (or a friendly one) from a half-mile away, and pokemon made of mithril are not easily slain. Domestic Lucario, however, are seldom buried; their trainers mourn as much as for any pokemon, but typically sell their corpses for scrap and use the money to swiftly train a replacement.
Lucario themselves carry forth the traditions of the heroic mithril-clad warriors of old. They fight not with swords and axes, but with spikes and claws, yet possess every bit as much courage and skill and use surprisingly similar techniques to boot. Indeed, fight scenes in fantasy movies at Pokestar Studios are often filmed with a well-dressed Lucario in place of the hero, despite the extensive makeup required for a Lucario to portray a human being. No matter how well a human stunt double can be trained, the way these pokemon battle far more resembles the legendary adventurers of old than do any of the human methods of combat which have survived into this age.