“Here’s what I know about underground rivers.”

When all four gathered around and tried to figure out exactly what has happened, all eyes were then turned to Wu who sat down on the sand and wiped his hand across to create a flat ground to draw on.

“Even among the largest desserts in my world, there are still lots of underground rivers or rather a water reservoirs.” Wu said, swiping his fingers across to draw up line after line of layers, “We have sand, then rocks that are permeable to water, and then the cavities underneath…”

“What are you suggesting…” Lera squatted next to Wu and looked at his drawing of what looked like a sandwich, “That there are holes underground?”

“Not just holes, but entire river systems…caves, and much more…” Wu said, “Or…sandworms. That’s just from some random stories, but after seeing Shrak’Ahk, I wouldn’t be surprised if that’s also another legendary beast just sitting here.”

“You felt it, haven’t you all?” Augen finally spoke, and he had only been listening to what Wu’s been saying without the ability to see the sand sandwich he drew, “If there’s anything underground, it’s not just water…”

“It felt like Wave.” Ver continued, “An insane amount of it.”

“Wasn’t that just from the bubble Cast?” Lera asked when Augen shook his head.

“No…” Augen leaned down to where he thought the diagram is and added another horizontal line across, “Water, and Wave. So much of it, that it can explain why there is nearly no natural Wave up at the surface level.”

Lera opened her mouth, but she had no clue how either of them figured it out. Ver noticed her look before placing a hand on her shoulder.

“It’s okay. At the instance of the bubble’s formation, an opening was created from this…underground river, and the Kraken, and I am sure Augen, felt it in that briefest moment before the bubble itself took over.”

Lera nodded, though she noted in her mind to practice Wave sensing in her spare time, if she were to keep up with her friends.

In the meanwhile, Wu knew full well that without a full set of Wave sonar, his make-shift visors and sensors wouldn’t be able to see past five meters of sand.

“So there is this rich underwater caving system with all this Wave…” Wu murmured, “You think that’s how Ilia traveled from the capital to here?”

“Not just that.” Augen shook his head, “I…wouldn't be surprised if that’s how everyone important travels. And it will be a lot quicker than trying to traverse through overground and worry about the Wave leaking from the chariot Casts constantly, while avoiding the weather.”

“Looks like we will be doing some excavating then,” Wu said, clapping his hands together. Then, he looked at Lera who’s eager to make a new Cast before turning towards Ver.

Then, his lips curved as he formed his hands into claws and strolled straight at the ex-mercenary as she stood on one leg and held her limbs in front in defense, “What are you thinking with that creepy smile…?”

“I think your abilities will be perfect for excavation.” Wu formed his hand into the outline of a sphere, “You suck in sand from the bottom, and you pour it out from the top. Augen, you can maintain a simple structure Cast with all of us in it, and Lera can be our guide with her Cast array. How does that sound?”

“You dare use the ability of a legendary beast as a tool?!” The Kraken’s voice came from within Ver when Wu, Augen, and Lera shared a glance of hesitation.

“Another hundred meters or so in our five o’clock direction!” Lera said as the small sphere of Wave, or their improvised capsule continued moving through the sand and rock layer with a surprising amount of smoothness, “An elastic shell of some sort…It felt weird, and my Wave lines are somehow bouncing off it!”

“I feel it too.” Augen added as he kept his hand on the surface of the spherical structure Cast with Wu sitting there with the visors over his eye.

He could see patches of glowing Wave lines coming from the hypothesized underground river, and he waited in anticipation when Lera’s expressions suddenly changed, and she gestured for Ver to slow down.

The sphere came to a gentle halt before Lera relayed what she felt through the Wave to Ver, who brought them closer to a soft elastic layer of materials that had the appearance of rock yet had color of egg shells.

“Let me take a look through it…” Wu said, reaching forward with his finger as a small dark column of Void Domain formed around his hand with activation from a button press. He then tore open a small circle in the shell with ease and the Wave contained within the materials moved apart as expected.

In that instance, purple light pierced through the hole he created, and it illuminated the insides of their sphere.

“What are you doing?” Ver asked when Wu created a spherical-shaped anti-Void Domain space before stuffing Lera’s Scouting Eye through it like a surgery happening in reverse. Then, they combined to create a full three-dimensional projection of the sights below.

It’s exactly as they expected, an underground river filled to the brim with Wave, illuminated by a mesmerizing purple glow all throughout, and it looked to branch out both horizontally and head deeper into the crusts of Olympus Prime. Strangely enough, this white soft material was the only thing holding back against the pressure of the sand, that's when Augen also reached down to touch it, only for it to stay stiff.

So this is a material that modulates its toughness through interactions with the Wave... Wu nodded slowly, quickly realizing that he hasn't actually seen anything like this before.

“I think you can take us down now, Ver.” Wu said, “There’s seemed to be no one here.”

“Then…here goes nothing,” Ver said, swirling her finger as the Whirlpool Purple swept up all four of them and teleported to the surface of the hip-deep underground river as Lera quickly tried to conjure up another structure Cast, but this time, the Wave lines were blown apart before the Cast was even fully constructed.

“Shit.” Augen cursed as all three of the Wave-sensing individuals dealt with the whip-lash of having to safeguard their Wave from leaking to protecting themselves from the overwhelming amount of Wave all around them in the depths of the river systems.

“Fu…fu…” Lera steadied her breath with rhythm pumps as Ver pressed into her temples. Then, they suddenly felt a wave of cold pass over them when Wu bound all of them within the Void domain.

That was a temporary measure, but from the look of relief on their faces, it was more than needed.

“I will reduce the intensity of the domain slowly, you all ready?” Wu asked, slowly lowering his hands and decreasing the intensity of the output from his Casts. At the same time, Lera refocused her efforts, thinking back to how everything felt back at the Academy before she recreated a bubble to contain everybody. Then, she added in a Void Domain shield layer just for good measure.

“That also explained why a dedicated capsule Cast may be necessary.” Augen said, “Just so people don’t have to deal with this…whiplash every time they move around.”

“But…look around you…” Ver said, and the four of them finally quieted down before taking a good look at the ethereal tunnels around them.

It was as if they had been invited to a whole new world, with the surface of the white rocky layers showing short glowing dark purple Wave lines that faded in and out of existence, and the purple light was indeed the embedded lines of Wave from the cave walls all around them and the riverbed under their feet.

If the base of the Titan’s spine had fuel rocks that behaved like concentrated pockets of the Wave which can be dampened by the presence of Water, then whatever chemistry’s going on right here in these waters…is something entirely different.

Wu poked his finger out through the shields and tapped the surface of the cool reflective water, then, he tasted it, as any stupid human would.

It tasted like regular ol water, but it was different than what he had been drinking on the Eastern continent, certainly different than the springs in the Endless woods, yet…he couldn’t quite describe what the differences are. The water here tasted a little softer, a little sweeter, and…

“Someone’s coming!” Augen warned before Ver and Lera also caught a hint of the shifting Wave locally.

The sounds of water slushing accompanied by the rapid movement of the incoming capsule immediately spurred Ver to Whirlpool all of them into a shadow in the wall as they looked out through a tiny opening when a semi-transparent ellipsoid ball flew past from the surface of the water, as jolts of lightning connected the surface of the ellipsoid with the walls themselves.

“That…is freaking cool…” Wu murmured as the wake of the capsule’s rapid movement brushed past the air in front of them. He turned to Augen who was still trying to process everything in front of him, being the only one that interacted with the entire world through the Wave, “You once thought that Necrovia is lacking in the naturally occurring Wave, didn’t you?”

Augen nodded as Ver brought all four of them out into the Underground river once again, and he continued, “I never would have imagined that deep underground, they housed potentially the world’s most powerful resource…”

“A liquid version of Fuel Rock that is stable under such conditions…” Wu murmured, “We…we can do so much with this, Lera…”

“With this?” Lera tilted her head and looked at Wu as her bangs hang over her grey eyes.

“Yes.” Wu rubbed his hands together excitedly, “Ever heard of a thing called the internet?”

“Of course not.” Lera shrugged before looking at Ver, “Is that some sort of a fishing net?”

“Why are you looking at me for?!”

“Before you all get too carried away by the excitement.” Augen drew everyone’s attention yet again, “Since we know that this route is being used frequently, let’s see if it will help take us closer to the border towns.”