The Hearthome Gym is the fifth Gym challenged in Pokémon Diamond and Pearl and their remakes. While it is encountered before the third and fourth Gyms, Fantina is absent from the Gym until after the player has received HM03 (Surf) from Cynthia's grandmother in Celestic Town. In Pokémon Platinum, the Hearthome Gym is the third Gym.
Hearthome City Pokémon Gym Leader: Fantina
The Alluring, Soulful Dancer!
In Pokémon Diamond, Pearl, Brilliant Diamond, and Shining Pearl, the Hearthome Gym is a giant, five-story building constructed of gray stone blocks, and is illuminated by eerie gray-blue torches. On every floor, there is a simple mathematical puzzle and three doors corresponding with the answers. Picking the correct door leads to the next elevator up, while the two incorrect doors lead to a dead end and a Trainer to fight. The Pokétch has a Calculator App, which can be used to find the answers with minimal effort. The Gym Leader waits in the final room on the fifth floor, which has stained glass windows and resembles a cathedral.
In Pokémon Platinum, Hearthome Gym has become much like Dewford Gym from Generation III; it is dark, and the only light source is limited. The player must navigate their way around the Gym using a flashlight to locate a blue tile on the floor, which corresponds to the correct door. Entering the wrong door will result in the player returning to the lobby, and the blue tile is reset each time the player enters the Gym. Duskull lamps are used as visible walls, to guide the player around. There are other Trainers with flashlights the player must battle, in order to make their way to Fantina.
She is the third Gym Leader in this game, able to be battled on the first visit to Hearthome.
The Hearthome Gym first appeared in Dawn's Early Night!, where Ash and his Pokémon were ready to challenge the Gym Leader. Nando was there too, and, much to Ash's disappointment, he told him that the Gym Leader was away at the moment, and thus could not be challenged. After defeating Maylene and Crasher Wake at their respective gyms—the Veilstone Gym and Pastoria Gym—Ash and his friends returned to Hearthome City in Arriving in Style!, only to find out that the Gym was still closed.
Drifblim is Fantina's main Pokémon, having raised it since it was an Egg. It first appeared as a Drifloon in Playing The Leveling Field! where it was used in a practice battle against Ash and completely overwhelmed his team with Hypnosis before evolving into Drifblim.
After training, Ash returned for an official Gym battle where Drifblim proved to be more powerful than before, managing to put to sleep and knock out Pikachu and Buizel before being defeated by Chimchar.
Gengar first appeared in a flashback in Playing The Leveling Field!. It was the first Pokémon to be used during the Gym battle against Ash in Shield with a Twist!. Gengar went up against Buizel and Ash struggled against the quick Ghost-type, however Buizel was able to use the newly-developed Counter Shield technique and was able to defeat Gengar.
The Hearthome Gym debuted in Drifting Drifblim, where Platinum entered the Gym with Diamond and Pearl in order to challenge Fantina. After clearing the math puzzles, she made it to the Gym Leader's room, where the Gym battle begun. Using Diamond's borrowed Lax and her own Empoleon, Platinum was able to defeat Fantina's Duskull and Drifblim without too much trouble. Fantina then sent out Mismagius, whose hallucination powers immediately took effect. Having studied the three Pokédex holders, Fantina knew exactly what kind of illusions would be most effective against their Pokémon.
Thanks to the illusions, Mismagius was easily able to defeat Platinum's Empoleon and Ponyta, leaving her with just Lax. Against the gluttonous Pokémon, Fantina had Mismagius create an illusion of masses of food to distract it while the Magical Pokémon kept attacking it. Platinum was too confused by the illusions to fight back, making her chances of winning look slim. However, Pearl then noticed that Diamond, being a glutton like Lax, had no trouble with the food illusion, causing him to realize that Mismagius's illusions affect each people and Pokémon differently. Due to Pearl and Platinum's strong sense of reality, the illusions were causing them to have a headache, while Diamond and Lax had no trouble accepting the illusion and enjoying it. Upon realizing this, Pearl conveyed his findings to Platinum, who started playing along with Lax, much to Fantina's irritation. Just as Fantina was about to have Mismagius finish Lax off, the Big Eater Pokémon flung the Iron Ball it had been holding at Mismagius, defeating it and winning the battle for Platinum.
After the battle, Platinum revealed that she had chosen to use Lax in this battle due to Fling being a Dark-type move, and thus super effective against Ghost-types. Adding to the move's power was also the fact that Iron Ball (which the group had discovered earlier in Celestic Town) was the most powerful item to use Fling with. Also, thanks to the Speed drop provided by the item, Platinum had been able to turn Mismagius's Trick Room (which it had been using to create its illusions) to her advantage, allowing Lax to attack first. As a sign of her victory, Platinum was then awarded with the Relic Badge.
Duskull was first seen rescuing Diamond and Pearl after they fell off a pillar created Cyrus' Probopass. Fantina used her against Platinum's Munchlax in their Gym battle, where she was easily defeated by Munchlax's Lick attack. She was later used to battle Saturn's Pokémon on the Spear Pillar alongside Mismagius.
None of Duskull's moves are known, and her Ability is Levitate.
Drifblim is the first Pokémon seen on Fantina's team and is her main mode of transportation. Drifblim first appears after Platinum wins her first Pokémon Contest where she throws the two women who attempted to sabotage her Contest in the trash. Drifblim is used to take Diamond, Pearl, and Platinum to the Lost Tower and later appears at the Celestic Ruins where she saves Diamond and Pearl's lives after they fall off of a stone pillar created by Cyrus' Probopass. Fantina used her in her Gym battle against Platinum where she fought her Empoleon, and despite putting up a good fight, was defeated when Empoleon used her Blizzard to freeze her. Fantina lent her to Platinum after she learned that her father had gone missing. Drifblim was later lent to Diamond who used her in a failed attempt to stop Team Galactic from capturing Mesprit. Drifblim returned to her Trainer when the Gym Leaders arrived to confront Cyrus at the Spear Pillar.
Mismagius is Fantina's strongest Pokémon and main battler. Mismagius was first seen watching Fantina's Drifblim throw the two women in the trash after they attempted to sabotage Platinum's Contest challenge. She was used to battle Platinum in her Gym battle and she fought the Munchlax she borrowed from Diamond, using her powers to create powerful illusions before eventually being defeated by his Fling. She was later used to battle Saturn's Pokémon on the Spear Pillar and later fought Cyrus in order to destroy the first Red Chain.
The Hearthome Gym made a brief appearance in Dialga's Secret Keys, showing Hareta earning the Relic Badge from Fantina.
Trivia
Although the Hearthome Gym is the third in Platinum, it still shows up as the fifth Badge on the Trainer Card and Fantina's face is on the fifth slot.
The Gym in Platinum bears a striking resemblance to the Battle Pyramid, as the lighting there is also limited and a blue tile must be found to continue.
The inner part of the area where the Gym Leader stands usually is a color that corresponds with the Pokémon type that the Gym's theme is, but in Platinum, Fantina is standing on an orange inner ring rather than the Ghost type's signature purple like she was in Diamond and Pearl. This may have something to do with the fact that in Platinum, the Hearthome Gym is the third Gym faced by the player rather than fifth like in Diamond and Pearl. The orange that Fantina is standing on is similar to the signature orange of the Fighting type, the type of the third Gym in Diamond and Pearl.
Both are the fifth Gyms of their respective region, and both Gyms are inaccessible the first time the player enters their city (though this is not true for the Hearthome Gym in Pokémon Platinum).
Both Gyms feature four sets of multiple-choice questions, and require the player to fight a Trainer if they answer the question incorrectly. However, the Lumiose Gym also requires the player to fight a Trainer even if the question is answered correctly.
Most of the Gym Trainers in both Gyms consist of young children and Ace Trainers.