Froslass first appeared under Candice's ownership in To and Fro with Froslass, where she sent her out as her second Pokémon during the Snowpoint Gymbattle against Platinum. She first faced Platinum's Rapidash, who was easily able to avoid most of Froslass's attacks. Even though Ice-type moves weren't very effective against Rapidash, Platinum had Rapidash heal himself with Rest just in case, only to be hit with a powered-up Wake-Up Slap from Froslass, severely weakening him. Froslass was then recalled as Candice sent out Abomasnow. After Abomasnow had been defeated by Platinum's Lopunny, Candice sent out Froslass once again. Even though Froslass seemed to defeat Lopunny rather easily, the Snow Land Pokémon was then defeated by a surprise attack from Rapidash, who had secretly been restored by Lopunny's Healing Wish, making Platinum the winner of the battle and earning her the Icicle Badge.
In Double Trouble with Dialga and Palkia I, Froslass joined Abomasnow and the Pokémon of five other SinnohGym Leaders' Pokémon during the final battle against Team Galactic at the Spear Pillar. Although the Gym Leaders were able to defeat the three Commanders and destroy one of the two Red Chains that Cyrus used to control Dialga and Palkia, they were unable to stop the Temporal and Spatial Pokémon from fighting each other, and were subsequently defeated by Cyrus's Pokémon. As the Gym Leaders themselves were unable to fight anymore, they gave some of their Pokémon to Platinum, including Candice giving her Froslass to her. Unfortunately, a blast from the two Legendary Pokémon's battle damaged the Poké Balls containing Platinum's new Pokémon, preventing her from using them at the time.
After the crisis with Team Galactic had been cleared, Platinum's new Pokémon were seen being treated by Daisy in Tackling Togekiss. After they had fully recovered, Daisy deposited them into Platinum's PC Box. Later Froslass, along with Platinum's other Pokémon, was sent to Stark Mountain to help Looker and Buck while she challenged the Battle Factory After Platinum had successfully defeated Thorton, Platinum's Pokémon returned with Looker and Buck, who had been severely injured while facing Charon and Heatran at Stark Mountain.
After the two men had been taken to a hospital to be taken care of, Platinum challenged the Battle Hall with Froslass. In Dealing with Dragonite, after having made her way through an exhaustingly long streak of 169 battles, Platinum finally faced Argenta, whose Pokémon was a Dragonite. Despite having a notable type advantage, Froslass still had a tough time battling against the Dragon Pokémon, taking heavy damage from its Steel Wing. However, thanks to the Babiri Berry Platinum had given to Froslass to hold, she was able to survive the attack and defeat Dragonite with Ice Shard, earning Platinum the Hall Print.
Having once belonged to a Gym Leader, Froslass is a well-trained and strong Pokémon. During the battle against Argenta, Platinum mused how she had originally faced Froslass as an opponent, but through the dozens of battles she went through with her at the Battle Hall, she came to know her a lot better. The two have a close relationship after battling so long together.
Candice's Pokémon Cards listed with a blue background are only legal to use in the current Expanded format. Cards listed with a silver background are legal to use in both the current Standard and Expanded formats.