This marsh lake had never originally existed on Route 114.
It had been created by Sato for one simple purpose—to provide Swampert with the ideal environment to advance to the Elite Four level.
The marsh lake was rich in both Water-type and Ground-type energy. For Swampert, who possessed both attributes, there could hardly be a more suitable place to undergo his breakthrough.
As for why Sato had chosen to begin the energy infusion in the middle of the night, the reason was equally straightforward.
The process of energy infusion was extremely dangerous.
It could not be interrupted by outside disturbances, or it could easily fail midway, leaving the Pokémon seriously injured.
Now, in the stillness of the late night, it was the perfect time for Swampert to begin.
In fact, to ensure that Swampert wouldn't be disturbed during the process, Sato had spent the past several nights guarding the marsh lake himself. Whenever a wild Pokémon approached, he would immediately have his own Pokémon drive it away.
He had even instructed Swampert to battle every powerful wild Pokémon within several kilometers, defeating each one in turn so that the local wild Pokémon would thoroughly understand that the newly formed marsh lake belonged to Swampert.
By now, Swampert had become the undisputed little overlord of the surrounding wilderness.
Had Sato permitted it, numerous wild Pokémon would already have gathered around him, willing to become his followers.
After all, following several days of energy infusion, Swampert had already begun to emit a trace of an Elite Four-level Pokémon's aura.
In the wild, that alone was enough to establish him as a regional ruler capable of gathering followers and claiming territory.
"Let's begin, Swampert."
Suspended cross-legged in midair by his psychic power, Sato spread out his psychic senses and quickly swept over the entire marsh lake.
After confirming that everything was in order, he spoke to Swampert below through telepathy.
Swampert nodded.
He slowly closed his eyes as an increasingly powerful aura radiated from his body.
Soon, black markings gradually appeared across his skin, while behind him a phantom image of Kyogre materialized.
The moment the phantom appeared, it let out a silent roar.
Immediately afterward, a strange wave spread outward from Swampert.
Within moments, every Pokémon within several kilometers awoke in alarm before trembling fearfully where they lay.
Those that had wandered close to the marsh lake fled in panic, racing as far away as possible.
"That should make things foolproof."
"Come out, Kadabra. Stay here with me and help protect Swampert."
Satisfied after seeing Swampert release his Legendary aura to intimidate the surrounding wild Pokémon, Sato released Kadabra to stand guard alongside him, ensuring that nothing interfered with Swampert's breakthrough.
Soon afterward, Swampert truly entered the energy infusion stage.
In his left hand he held the Mystic Water.
In his right hand, he gripped Groudon's Blood.
Under Swampert's guidance, both treasures erupted with astonishingly pure elemental energy.
At first, the two streams of energy behaved like wild horses that had broken free of their reins, darting chaotically through the air.
One was Water-type energy.
The other was Ground-type energy.
As opposing attributes, they immediately began clashing violently with one another.
However, thanks to Swampert's masterful control over both Water-type and Ground-type energy, the two opposing forces eventually had no choice but to submit.
Like extensions of his own arms, they obediently circled around his body according to his will.
Each complete circuit around Swampert caused both streams of energy to shrink slightly.
Yet almost immediately, fresh energy surged from the Mystic Water and Groudon's Blood, replenishing them back to their original size.
At the same time, tiny traces of black impurities seeped out from Swampert's body.
His aura grew just a little stronger.
The increase was nearly imperceptible at first.
But as the cycles continued...
...the change became increasingly obvious.
The oppressive presence unique to an Elite Four-level Pokémon gradually began emanating from Swampert. However, as the number of circulation cycles increased, Swampert's condition worsened dramatically.
His skin turned completely crimson, like a fully cooked lobster.
His face twisted from the intense agony raging throughout his body.
Clearly, although the energy infusion was making him stronger, the pain required to obtain that strength was unimaginable.
Even with Swampert's iron will, after nearly an hour of continuous infusion, he was beginning to reach his limit.
"That's enough, Swampert."
"Stop here for today."
"Don't rush it. Take it one step at a time."
Sato had kept almost all of his attention focused on Swampert.
Seeing that Swampert was about to collapse but was still stubbornly enduring the pain, he gently called out to him.
The process of energy infusion was never something that could be completed overnight.
Swampert had only begun undergoing it a few days earlier.
Even so, what surprised Sato was how astonishingly fast Swampert's progress had been.
Ordinary Pokémon, even under ideal circumstances, required at least two or three months to complete an energy infusion.
Swampert was different.
His progress was astonishing.
In just a few days, Sato estimated that he had already completed a small portion of the entire process.
The progress of energy infusion could actually be observed directly through a Pokémon's body.
To put it simply, the process was one of tempering the body itself, raising its physical capabilities to an entirely new level.
Because of that, Trainers could judge a Pokémon's progress simply by observing which parts of its body glowed during the infusion.
After several days of training, Swampert had successfully completed the tempering of part of his right leg.
Sato estimated that in only a few more days, the entire leg would be fully tempered.
At that point, Swampert's right leg alone would already possess the durability needed to contend with the physical strength of an Elite Four-level Pokémon.
"Swamp~"
Swampert had always faithfully carried out Sato's instructions.
He slowly ended the energy infusion.
The Mystic Water and Groudon's Blood in his hands gradually ceased releasing energy.
At that moment, the Mystic Water had noticeably lost much of its luster.
Meanwhile, Groudon's Blood had visibly shrunk by an entire size.
Clearly, after supplying Swampert's energy infusion for several consecutive days, both treasures had already expended a significant portion of the elemental energy stored within them.
Groudon's Blood wasn't a major concern.
It was still roughly the size of a fist and looked capable of lasting for quite some time.
The Mystic Water, however, was nearing its limit. Its quality had deteriorated drastically.
In only a few more days, it would probably become nothing more than a useless relic.
"The amount of elemental energy required for energy infusion is simply staggering."
"No wonder advancing to the Elite Four level is so difficult."
"Without treasures containing such dense elemental energy, relying solely on absorbing energy from the surrounding environment... who knows how many years it would take?"
"Fortunately, the Elite Four-level Trainers gave me quite a few Mystic Waters this time."
"Otherwise, Swampert's progress would have slowed down again."
"They're veterans, after all."
"They must have known I'd eventually run short on treasures like Mystic Water, which is why they specifically gave me so many."
Looking at the high-quality Mystic Water in his hand—the one he had once purchased at a tremendous price, whose surface had now become almost completely dull—Sato couldn't help letting out a quiet sigh.
As soon as Swampert finished today's energy infusion, Sato immediately recalled the exhausted Pokémon into his Poké Ball.
Then, together with Kadabra, he repeatedly used Teleport to head toward the Pokémon Center in Fallarbor Town.
After successfully completing an energy infusion, a Pokémon's mental state would inevitably be utterly exhausted, and its body would also suffer varying degrees of damage.
At times like this, professional medical care was essential for a full recovery.
That was something Sato couldn't provide himself.
So once again, he would have to pay a late-night visit to the Nurse Joy who had recently been complaining about his frequent midnight arrivals.