Lucario debuted in DP110 at Iron Island. When Ash and his friends traveled there after being contacted by Jun, they found the local Template:Type2 Pokémon fighting brutally against each other and the other Pokémon on the island. When a crazed Aggron attacked Ash, Riley stepped in and had Lucario attack it with Close Combat. Despite being a Steel-type as well, Lucario didn't seem affected by whatever was driving the other Pokémon mad.
Riley informed Ash that like his Lucario, he could use Aura. Together they found the source of the problem: A machine operated by a Team Galactic outfit under Mars's command that was using the Spear Key to create radio waves which tortured the Template:Type2 Pokémon. Lucario attempted to read the Aura coming out of the machine, but at that time, Mars placed the Spear Key into a pillar at the ruins the squadron was excavating. The beam that launched out of the pillar's tip overwhelmed Lucario and caused it to rebel against Riley, even breaking its Poké Ball in half when he tried to recall it.
Even then, however, Lucario wasn't completely under the machine's influence and soon attacked and destroyed it, afterward regaining composure. When Mars realized her plan was shot, she fled and attempted to blow up Iron Island with a number of Galactic Bombs, but her efforts were thwarted when both Riley and Lucario used their Auras to contain the blast.
Moves used