Honestly, with the nanotech and liquitech they had, building up a series of tests wasn't all that hard. They had quite a few facilities that had long since become redundant, so cannibalizing the materials and recycling them was short work.
"You ready for this, Vahl?" H'El said over the comms.
"Yeah. Flip the lights."
In the underground tunnel they constructed, powerful lights lit up. To anybody else, they would be blinding white. To an empowered Kryptonian, they were deep red.
"Nus der."
An artificial star appeared over Vahl-Or's head, further blocking his power.
"Are you sure this is a good idea?"
"We need to know what this Speedster power is capable of. That'll be easier if I don't have to consciously hold back my solar abilities. Start the timer."
Calling upon the new energy, Vahl-Or felt the crackling over his body. It was strange how natural this felt. Other energies absorbed always felt wrong at first, or at least took a while to call upon. Even new solar abilities had taken a while to control.
As he heard the click of the timer, he took off...
And slipped halfway through.
BLAM.
"Woah, 27.2 miles in less than two seconds. That's amazing! Let's run that a few more times, see if we can improve it.
... Vahl?"
"Put in the file that the energy may emit a friction-cancelling aura."
"You slipped and slammed into the wall, didn't you."
"Yes."
"...I'm saving the footage."
"Please don't."
"You'll laugh with me later!"
"I hate you. Also, turn off the dampeners."
(AN: Vahl-Or and H'El are speaking Kryptonian and using Kryptonian units of measurement. I, however, do not feel like making up names for measurement.)
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Turns out, the speed energy also gave a healing factor. Unfortunately, unlike his solar healing, it didn't break down misplaced bone shards and reform the cells in the proper place.
To answer the unsaid question, yes, rebreaking your own bones so they'll heal properly hurts. A lot.
"So, this is to test out the phasing?"
"Yes."
"What if you unphase early?"
"Wouldn't be the first time I got stuck in a wall."
Unlike the first test, this would be done without dampeners. He did not want to end up in the planet's core, so he would stay flying until the test was over.
He got through the third wall before he lost focus.
Good news, he wasn't stuck in a wall.
Bad news, the flying shards broke the sound barrier, wrecking most of the area.
"So that's why I'm not in there with you."
"Yeah. Didn't want to find out if I unphased with your hand inside me."
"That sounds rather suggestive."
"By Rao, H'el, get your head out of the gutter."
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Vahl-Or and H'El stared at the new canyon in front of them.
"I told you this was a bad idea, H'El."
"Oh, come on!"
"Vibrating Heat Vision! Why did I let you talk me into that?!"
"It's not that bad, Vahl."
"That was a low-power blast meant to just warm people up when they're cold!"
"I, well... at least we're on New Wegthor?"
"Yes, cause damaging the artificial moon that took me YEARS to make is that much better."
Needless to say, they weren't combining speed energy with anything other than flight.
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H'El groaned from his hole in the wall.
"Okay, absorbing the speed energy only gives a temporary usage. Permanent connection likely requires energy equivalent to that which the Flash used against me. Which may or may not kill the absorber if they are not powerful enough to withstand it."
"You're enjoying my suffering, aren't you, Vahl."
"Yes, very much so."
"Love you, too, bestie."