In fact, on Route 209, there are two places that are worth exploring, namely the Lost Tower and the Hallowed Tower
Hallowed Tower is the Sinnoh region's only location where Spiritomb can be encountered. Cynthia's Spiritomb was captured here.
Spiritomb is a Ghost/Dark-type Pokémon with excellent defensive attributes. It is immune to Normal, Fighting, and Psychic-type moves. It takes half damage from Poison-type attacks, and only Fairy-type moves deal super-effective damage to it.
However, it must be noted that the Fairy-type has not yet been formally recognized as an official type classification. This means that, at present, Spiritomb has no weaknesses.
Cynthia's Spiritomb possesses a unique ability—when it uses Psychic, it can temporarily immobilize its opponent. It was precisely this unusual trait that allowed Cynthia to capture this peculiar Spiritomb in the first place.
Aside from the Tower of Soul, the Hallowed Tower serves a similar purpose to Mt. Pyre in the Hoenn region. It is a burial ground for many deceased Pokémon in Sinnoh, and as a result, it is filled with numerous Ghost-type Pokémon and residual Ghost-type energy.
Mt. Pyre is maintained by two elders and contains a hidden training area left behind by a legendary Pokémon, which keeps the Ghost energy there under control. The Hallowed Tower, however, lacks such safeguards, leaving its Ghost energy in a chaotic and unstable state.
Recently, the Sinnoh League has prohibited further Pokémon burials within the Hallowed Tower and has temporarily classified it as a restricted zone, barring entry from unauthorized individuals.
As such, Aoki merely passed by these two famous towers without entering.
By the time Aoki neared Solaceon Town, the sky had already darkened.
Since Route 209 is an official League-maintained path, there are few powerful wild Pokémon along the way. Aoki primarily used his Drapion as a land mount, while his real battles were handled by his Aron and Larvitar, neither of which had seen much action recently.
Surprisingly, the combined force of these two heavy-hitting Pokémon proved quite formidable.
Almost no wild Pokémon could withstand their coordinated assaults.
Given Aoki's walking pace, he wouldn't reach Solaceon Town before nightfall, but this posed no issue for him, as he was accustomed to camping in the wild.
However, setting up camp directly beside a League highway wasn't ideal.
So Aoki turned onto a smaller side path instead.
The Sinnoh region is dominated by Mt. Coronet, but it is also surrounded by numerous smaller foothills.
Aoki's goal for the night was the first of these hills, not far from the main road. He hoped to find a natural cave there—and if not, he could always have his Drapion dig one out without much trouble.
Perhaps due to the approaching night or the remoteness of the path, the strength of the wild Pokémon in the area gradually increased.
Aoki recalled Aron and Larvitar, then sent out his Marshtomp and Poliwhirl instead.
Since these two Pokémon were being prepared for the Sinnoh League, and since Aoki was a Water-type Gym Leader, it made little sense for him to rely on only one Water-type Pokémon. They needed to gain experience quickly.
That said, rapid growth came with its own risks.
A sharp increase in strength often led to an unstable foundation. While this could be corrected with further training, doing so would require significant time and effort.
For now, Aoki had no choice but to have them battle frequently, gradually smoothing out their weaknesses to meet the standards of the Sinnoh League.
After some consideration, Aoki released his third Pokémon—his Florges.
Florges had nearly fully recovered, though she wasn't quite at her peak yet.
She was a guaranteed participant in the upcoming Sinnoh League, but as a newly evolved Pokémon, she still needed to adjust to her evolved form's capabilities. Aoki summoned her so she could familiarize herself with her enhanced powers.
With these three Pokémon accompanying him, Aoki ventured deeper.
The Sinnoh region housed many Pokémon that were unfamiliar to Florges, but just as many that she had battled before.
In truth, the number of Pokémon species native to Sinnoh was relatively small. Many of them were shared with other regions, with Sinnoh merely being the first to document their evolutions. As such, their Pokédex entries were registered under Sinnoh.
The most irritating Pokémon Aoki encountered along the way was the Stunky line—a species that emitted a foul odor from its body.
Not only was its stench unbearable, but as a Poison/Dark-type, it was only weak to Ground-type moves. All other attack types were either resisted or ineffective.
Additionally, this Pokémon was immune to Psychic-type moves and resisted Poison, Ghost, Grass, and Dark-type attacks.
Poison-types were already among the most troublesome wild Pokémon to deal with, making this encounter particularly unpleasant for Aoki.
Fortunately, Florges's strong supportive and healing abilities allowed Marshtomp and Poliwhirl to fight without restraint.
But… the smell was unbearable.
Absolutely revolting.
Thankfully, the ordeal didn't last long. After nearly an hour of travel, Aoki finally arrived at the base of the hill.
The saying "so near, yet so far" applied perfectly here—what had seemed like a short distance ended up taking far longer than expected.
At the foot of the unnamed hill, Aoki was fortunate enough to find a cave.
The cave showed no signs of habitation by wild Pokémon, which was unusual, as there were no traces of Pokémon activity in the surrounding area either.
Curious, Aoki cautiously stepped inside.
He pulled out a specialized torch, illuminating the strange cavern.
The interior appeared no different from any ordinary cave—except for one thing. It was impossibly deep, with no visible end.
Aoki walked further in, torch in hand, but even after some time, he couldn't find the back of the cave.
Unbeknownst to him, as he ventured deeper, several strange figures emerged at the cave's entrance.
They resembled symbols at a glance, but upon closer inspection, they seemed more like letters.
Yet each one had a single round eye at its center, making their true nature difficult to discern.
These figures were thin and clung to the dark stone walls, nearly invisible unless one looked closely.
As they detached from the walls, something bizarre happened—the cave entrance vanished, leaving only a faint indentation behind.
The figures exchanged glances with their large eyes before a small, zipper-like opening appeared in the mountainside. Inside, shadows and ashen mist swirled chaotically.
One by one, the figures slipped into the strange rift.
Once they disappeared, the opening sealed itself shut, leaving no trace of what had just occurred.