Maylene used her Riolu in her battle against Platinum. Riolu battled against Platinum's Monferno and Platinum's Chatot who were given by Pearl to Platinum to use in the gym battle. Riolu was first used against Monferno and it successfully dodged all Monferno's attack with its speed. It later used Force Palm on Monferno, slamming Monferno to the ground. It then directly used Drain Punch to absorb all Monferno's strength. Platinum switched Monferno out for Chatot and Chatot used Chatter to irritate Riolu. Maylene commented that Riolu's aura was emanating and that Meditite felt that Riolu was in danger. Maylene then switched Riolu out for Meditite. After Meditite was knocked out by Chatot, Maylene sent Riolu back out and easily knocked Chatot out with Vacuum Wave. Platinum sent Monferno again and Riolu and Monferno attacked each other at the same time. Riolu later used Rock Smash to crush the entire arena with rocks and moved with its speed through the rocks. Platinum used her slots skills that she had developed in the casino to sense where Riolu was. Platinum found Riolu and ordered Monferno to attack in the direction she sensed Riolu. Monferno successfully hit Riolu and knocked it out, making Platinum the winner of the gym battle.
Riolu and Meditite accompanied Maylene, who was going to see Candice at Snowpoint City. The two joined with Platinum, and were later confused to see her, despite saying she was going to Lake Acuity, having a Gym Battle against Candice. After the battle was over, Maylene, Riolu and Meditite joined Platinum and Candice, as they were going to Lake Acuity to stop Team Galactic's plans. Maylene sent Riolu at Lake Acuity, where they encountered a Sableye, who started to attack them. Riolu was hit by Sableye's Shadow Sneak; its trainer, Jupiter revealed herself to be Sableye's owner. Candice was hit by Jupiter's Gastrodon's Mud Bomb, so Maylene ordered Riolu to help her out. However, Riolu was hit by Gastrodon's Mud Shot before Riolu was able to help Candice. When Uxie emerged, Jupiter went to capture it. Maylene's Meditite used Power Swap, followed with Rock Tomb to attack Sableye. However, Sableye used Punishment, which defeated Meditite and Riolu.
Riolu and Maylene reappeared in Snowpoint City's Pokémon Center, despite Platinum remembering that she pulled everyone to Snowpoint Temple. To become stronger in the fight against Team Galactic, Maylene, Meditite and Riolu went with Platinum and Candice to meet up with Volkner, who would train them. Maylene confronted Team Galactic commanders at the Spear Pillar. She sent Riolu and Meditite, who teamed up with Abomasnow and Froslass, to battle Juputer's Pokémon. Candice and Maylene faced Jupiter, who had Tangrowth use Natural Gift. To stop it, Riolu fired Aura Sphere, along with Abomasnow's Ice Shard. The two sides exchanged blows, but Jupiter and Tangrowth were defeated. Since Cyrus was conducting his plans, space and time was being warped, so they could not reach him. The Gym Leaders went through the tunnels to get to Cyrus, and had their Pokémon attack the Red Chain to shatter it. Riolu was damaging the Red Chain, until it snapped. In fact, Riolu and the others shattered the fake, incomplete chain, leaving Cyrus to control Dialga and Palkia with the true Red Chain.
- ^ a b D&P050: Striking Out Snover
- ^ D&P019: Magnificent Meditite & Really Riolu I
- ^ D&P020: Magnificent Meditite & Really Riolu II
- ^ D&P051: To and Fro with Froslass
- ^ D&P058: Stopping Sableye
- ^ D&P059: Getting Past Gastrodon
- ^ D&P061: Tackling Tangrowth
- ^ D&P067: Encountering Elekid
- ^ D&P068: Shorting Out Electivire
- ^ D&P074: Double Trouble with Dialga and Palkia I
- ^ D&P075: Double Trouble with Dialga and Palkia II
- ^ D&P079: Double Trouble with Dialga and Palkia VI