Lorenzo led them through the museum's lower level and down a narrow stone staircase that opened into an underground waterway. The air was cooler here, the sound of moving water filling the space.
Latios moved to the front the moment they arrived, positioning himself beside Latias. The two of them looked at each other, and something passed between them without sound, a communication too subtle for anyone else to follow. Then Latios's eyes lit up blue.
Latias's did the same.
"Hold still," Ash said quietly to the others.
The underground waterway dissolved.
In its place, a river stretched in every direction, clear and deep, lit from above by filtered light. Water-type Pokémon drifted past in lazy arcs, Remoraid and Chinchou and shapes Ash didn't immediately recognise, all of them moving through water so clean it was almost invisible.
Jessie made a soft sound. Sabrina's expression opened into something genuinely surprised.
"It's beautiful," Sabrina said.
"Illusion Transfer," Ash said, reading the technique's psychic signature automatically. "Latios is transmitting his visual field directly to our perception in real time. What he sees, we see."
Lorenzo nodded. "You identified it quickly."
"It's a Legendary-tier technique," Ash said. "The mental output required to sustain a visual transfer across multiple recipients simultaneously isn't something a standard Pokémon can replicate. Even my Gardevoir couldn't manage it."
Sabrina glanced at him sideways. He could feel her filing that away as a personal challenge for later.
...
In the illusion, Latios moved deeper into the waterway, his streamlined body cutting through the current with the easy precision of something built for exactly this environment. The water around him was mostly clear.
Mostly.
"There," Ash said.
He'd caught it at the edge of the visual field, a gradient so gradual it would have been easy to miss without knowing what to look for. The water further ahead was darker. Not dramatically, not visibly polluted, just slightly, persistently wrong in a way that registered as off rather than dangerous.
"You see it," Lorenzo said, less a question than a confirmation.
"Two years of gradual weakening," Ash said. "The blackening is spreading outward from the center." He watched Latios navigate toward a section of canal wall that looked solid and unbroken. "What's through there?"
"Watch."
Latios passed directly through the wall without slowing.
James made a sharp noise. Meowth grabbed his arm.
"It's a projection," Ash said. "The wall is a false surface. Aura reading confirms the entrance is there, it just looks solid. Realistic enough to fool a casual observer, but the density reading is wrong."
Beyond the false wall, Latios had stopped.
The space on the other side held a stone platform mounted with an ancient disc, its surface carved with symbols that predated anything in the modern Pokémon League's historical records. At the center of the disc, raised on a plinth shaped loosely like a trophy column, sat a crystal sphere the size of a fist.
It was emitting white light. Faintly. Less than it should have been.
"The Soul Dew," Ash said.
"Yes." Lorenzo's voice had shifted, quieter now. "Two years ago the light began to dim. The rivers near the center of the city have been darkening since. Slowly, but it's accelerating."
Ash looked at the sphere for a long moment, reading what his Aura could reach through Latios's visual link.
Then something else clicked into place.
"The two children Latios brought with him," he said. "The ones who disappeared from the legend after the battle." He turned to Lorenzo. "Your great-grandfather adopted them."
Lorenzo didn't deny it. "You worked that out from the gaps in the intelligence report."
"The information James collected didn't mention them at all. That kind of omission doesn't happen by accident." Ash looked at Latias, who was watching him with wide, still eyes. "They were Latios and Latias. Your great-grandfather raised them after their father died."
Lorenzo exhaled slowly. "Yes. The Soul Dew was made from their father's soul, at the cost of everything he had. It's been protecting this city ever since." He folded his hands. "But it's fading. And I don't know why, or how to stop it."
The illusion held around them, the underground river turning slowly, imperceptibly darker in the distance.
Ash was quiet for a moment.
"I think someone's already been here," he said.