Because the DC Universe is infinitely confusing with an extraordinarily large amount of different versions of each superhero, I'm going to go with what's most convenient and easy for most characters.
For the Flash, let's just use the CW show as reference and say Barry works with Cisco and Caitlin in Star Labs for his night job and is a forensic scientist for the police as his day job. No further questions, please. It'll get too complicated and messy if we get too deep into the hows and whys. Just sit back, suspend your disbelief a teeny bit, and enjoy.
Scienthology
noun.
The theory that even in the most fantastical myths, science holds true. Logic stays firm, and there is always a reasonable explanation.
Percy's mouth was twisted in the shape of a slight frown. Despite the sweet aroma of sugar and the familiar scent of freshly ground coffee beans, he was still a little annoyed. With a glance at the clock on the opposite wall, he confirmed to himself that his hopeful acquaintance was indeed running 15 minutes late.
His foot tapped erratically and unrhythmically on the tile below. He tried to distract himself by watching the people around him, but his eyes continued to stray towards the coffee shop's clock every few seconds. He was tempted to go outside and double-check that he was at the right place, but he knew he was where he had to be. Central City Jitters was indistinguishable.
Just at the name, Percy's nose scrunched up in annoyance. It wasn't that Jitters was a bad coffee shop, not by any means. It wouldn't be as popular if it had been. But… after spending months working for a local café in a niche city in Colorado, he had more than a little pride in his work and the quality of his product.
Man, for being labeled the fastest man alive, Barry Allen certainly wasn't the most punctual.
A flash of light that Percy almost failed to notice quickly appeared in front of him and before he could even blink in surprise, a man with a sheepish smile and a coffee in one hand was in the seat opposite of him.
"Sorry I'm late!" The man breathed out. He took a large gulp from the plastic cup in his hand and sighed in satisfaction. "I had a breakthrough on the case I was working on and kinda just lost track of time."
"It's alright. I'm honestly surprised I arrived on time myself," Percy admitted. "Barry Allen, I assume?"
"You assume correctly. " Barry tilted his head in a slightly awkward bow. He chuckled and shook his head in amusement. "I don't think I've arrived on time to something in the past 2 years. Sorry again about that."
"It's alright man, I get it," he responded good-heartedly.
"Thanks," Barry grinned. "Down to business, I guess. Diana vouched for you and told me that you wanted to talk a little bit, but she didn't exactly say what about."
"Yeah, so I read an interview that you did about how you had to learn how all your… you know - powers - work, and I was wondering how you did that." Percy said, whispering slightly at the end in fear of people around them overhearing something they shouldn't overhear. "I know there are things that I might be able to do, but I don't exactly know how to do them."
"Ah." Barry clicked his tongue and nodded. "I see. This is probably better if we take this somewhere else, then. Wanna step outside?"
"Sure," he said. The two of them stepped out of the shop with Barry tossing his somehow already empty cup of coffee into the bin.
"Do you get nauseous at all?" Barry asked once they were outside. "Car sick, sea sick, anything like that?"
"Not really, no."
"Good." Barry firmly clasped Percy's shoulder with his hand. "Try not to move."
Before he could get a single syllable out in questioning, he felt a sensation so foreign and strange that was almost too difficult to describe. It felt like his body was being ripped in half, but at the same time, he didn't feel any pain. He felt something akin to the most powerful burst of wind he'd ever experienced fly by him.
Before he could even begin to process the sensation, it was already over, and Percy was left regretting the rather large lunch he had eaten. Black spots danced in his vision and his stomach was left curling around itself. His head spun in circles, but before he could stumble around and search for something to stabilize himself with, he found himself grasping the edges of what he concluded to be a gray trash can.
"Thanks," Percy gasped out to whoever had slid him the object.
"You alright man?" Someone responded. The words were dulled and fuzzy to his ringing ears, but he nodded anyway.
"I'm fine," he said. He inhaled sharply and exhaled deeply. "Just gimme a couple of seconds."
"Take your time," the voice said generously. Again, Percy nodded. He began to focus on his breathing, and within a minute or so, his vision had balanced and his body for the most part had returned to normal.
"Okay. I think I'm good," he breathed out. After a moment, he couldn't help but chuckle. "I'm guessing that happens a lot?"
"Most people throw up, to be fair." Barry said. Percy looked up to find two more people standing besides Barry - a man and a woman, both with dark hair. "You honestly did pretty well."
"Thanks." Percy said dryly. He then noticed the new setting they were in and frowned curiously. "Where are we?"
With a quick spin, Percy soon realized that he should probably keep his hands from roaming. Practically everything in sight looked expensive and modern. From large monitors spanning the curved walls to desks cluttered with assuredly pricy science equipment to even the mannequin donning a red and gold suit.
"Welcome to S.T.A.R Labs!" The man besides Barry proclaimed, spreading his arms in a welcoming gesture. "I'm going to assume that you're one of Barry's friends from his special club, right?" The man cleared his throat loudly, cocked his head and looked at his superpowered friend pointedly, who nodded with a humored grin.
"Excuse Cisco and his terrible manners. I assure you that his parents raised him perfectly fine until he forgot everything they taught him." The woman said with a smile. The man exclaimed at that, seemingly offended. "My name's Caitlin."
"Percy," he responded in kind, shaking her proffered hand firmly. Drawing from the fact that neither Cisco nor Caitlin had reacted strangely to his and Barry's arrival, he concluded that they were trustworthy. And, well, there was a mannequin with the Flash's suit in the room for all eyes to see, so that said something as well. "And I'm not part of the Justice League. At least, I don't think so."
"You're not. But I wouldn't be surprised if it happened someday, not with the way Diana talks about you." Barry said.
"She talks about me?" Percy's eyebrows raised. "Should I be worried?"
"Maybe a little bit," he admitted and shrugged a single shoulder. "It's all mostly good things."
"Mostly?" If it was possible, his eyebrows raised even higher.
"Uh…"
"Okay!" Caitlin said suddenly, perking up with a smile that probably saved Barry from any awkward explanations. Percy mentally reminded himself to thank her later. "How can we help you, Percy?"
"Oh, right!" He repeated what he'd said to Barry earlier in the coffee shop, and by the time he was finished with his rough explanation for what he was curious about, the woman was practically smiling from ear to ear.
"We'd love to help." Caitlin said. "All three of us are scientists in different fields, so we'll all have different perspectives on how your abilities might be utilized."
"Cool." Percy said honestly. "So… how do you wanna do this? You gonna put me under a microscope and do a bunch of tests on my body?"
Barry laughed and shook his head humorously, "A demonstration might be best to do first."
"Oh." Percy frowned. "That makes sense."
"I must say, I'm curious about what you can do. The way Diana hyped you up, I'm kinda excited." Barry said.
"Don't get too excited." Percy warned humorously with a timid smile. "Should we go anywhere or do you need to prepare anything?"
"Perhaps later." Caitlin said. "If you don't need any tools or specific environment to use your powers safely, then you can start whenever you're ready."
"Cool." Percy headed to the middle of the room. He paused. "Actually, a bottle of water might be nice."
"Barry." Cisco prompted, the corner of his lip twitching in humor. The speedster rolled his eyes, but nonetheless turned into a blur for only a second before returning right where he had left with a stainless steel water bottle in hand. Percy had to say that he much preferred watching him run than being pulled along with him.
"Here." Barry casually tossed the bottle to Percy, who sloshed the water around once caught. He nodded in acceptance, noting the bottle was a little less than full.
"Thirsty?" Cisco asked, sitting up in his chair and scooting forward to attention. Percy chuckled
"Something like that," he said. He tossed the bottle between his hands, feeling the cold steel against his fingertips but more importantly feeling the liquid within. It wasn't accurate to say it was full of life, but there was an energy that he could feel.
It was pure, and it felt like it was a part of him, strangely enough. More than when he was younger, he felt more in tune with his father's domain. He felt more aware of the water that was all around him, whereas before, when he was a teenager, he didn't have that same consciousness. It was… an odd feeling to describe. Something that now felt like second nature, something that he was constantly subconsciously aware of.
"Here." Percy flipped the bottle in his hand and nodded towards Cisco. "Catch."
"But you didn't even-" Cisco yelped as the silver object came flying towards his head at an uncatchable speed. His hands went up to cover his turned head, bracing for impact rather than even attempting to catch the bottle.
The impact never came, and when the man hesitantly uncurled, he found that the bottle was floating in mid air.
Barry whistled in approval, an amused smile gracing his face.
"Amazing." Caitlin peered at the floating object closely before turning to note Percy's outstretched palm. She made her way around the desk and after circling the floating bottle, carefully poked it. Despite shifting an inch or so from the force of her finger, the bottle stayed strong and unmoving."Telekinesis? Or perhaps precise control of metallic alloys?"
"Not quite." Barry commented from the side.
"Almost." Percy shrugged. He nodded toward the bottle. "Could you unscrew the lid?" With practice, Percy could probably eventually be able to uncap the water bottle, but that type of precise control and force wasn't something he was going to attempt right now.
After Caitlin unscrewed the lid and let the bottle go, Percy slowly levitated it down onto the desk and with a simple upturn of his index finger, shot the contents of the bottle into the air above.
Cisco practically fell out of his chair when he saw the floating water in the shape of a miniature lightning bolt. Deciding to test his limits and show off just a little bit, Percy even added small lightning effects with flicking water particles.
"'Not quite' is an understatement." Cisco practically whispered, now fully stood up and staring with wide eyes at the spectacle before him. Percy failed to stifle a chuckle. "Is it just liquid?"
"All forms of water." Percy said. He paused, then shrugged. "Or at least, that's what I think. I was hoping you guys could help me with that."
"How did you lift the bottle if you were only telekinetically controlling the water?" Caitlin asked. "Granted, I don't know exactly how your powers work yet, but it seems like that would at the very least take an immense amount of effort."
"To be honest, I don't really know." Percy said, cocking his head in thought. "I made it so that the water fitted to the bottle like a kind of inner shell, and then I guess I hardened the water, if that makes sense? That might not be exactly what I'm doing, but that's the best way I can explain it."
"Hmm." Caitlin frowned. She reached up and sifted a finger through the water-made replica of the Flash's logo. The water made way for her finger, yet returned to its original, free-flowing position once she'd gone all the way through. "Do you know how you obtained these powers? It might be easier to understand what you're doing once we know how this is possible."
"Uhhh." Percy bit his lip in hesitation and looked at Barry. Diana had told him that Barry was to be trusted, and that his judgement was most usually correct. The knowledge of the gods' existence was esoteric and prudent to a few, but in this instance, it might be necessary. "You trust them, right?"
"With my life," Barry nodded.
"Alright then." Percy took a deep breath. He laughed and threw his arms out in a gesture that really just said "fuck it". "This is gonna take a little bit."
By the time Percy was done with his whole explanation, Cisco was slouched in his chair and staring blankly up at the ceiling while Caitlin was peering at him disbelievingly with her eyes the size of small slits.
"Honestly, I wouldn't believe me either." Percy laughed. "If you want to take a blood test, I'm sure you'll find something that gives credence to it."
"Well, it's not exactly that we don't believe it-" Caitlin frowned.
"I don't believe it," Cisco interrupted abruptly.
"-It's just that I don't understand how that would be scientifically possible." Caitlin said. "All of the seemingly impossible encounters we've had have been scientifically explainable. But… gods?"
"Greek gods." Cisco stated helpfully, still staring at the ceiling and seemingly in a shocked daze.
"And Roman gods, although that's a little confusing." Percy added. He thought for a moment more before he clicked his tongue. "And Egyptians. And Norse."
If possible, Cisco and Caitlins' eyes widened even further.
"Well…" Caitlin sputtered a breath and smiled. "Let's get started, shall we?"
Percy grinned, "Sounds good to me."
A handful of minutes later and after a generous amount of convincing from Caitlin that that giant pointy metal thing sucking blood from his arm wouldn't be that bad, Percy found himself lounged in a chair with a bandage on his arm. He was actively trying not to look at the place where the scientist had extracted an admittedly small amount of blood from him, and Cisco did him the favor of distracting him with questions while Caitlin prepared to study his blood.
"So you've controlled liquids that aren't fully water before, right?" Cisco recapped. "And you've even controlled other forms of water, like ice and snow?"
"Correct." Percy nodded, his vision trained on basically everything but the bandage on his arm. Needles were worse than Kronos and Polybotes combined, he swore. If a bane of Perseus Jackson existed, it wouldn't be any Gaea-serving giant; it would be needles. "But my control over liquid is stronger."
"Okay, that kinda makes sense." Cisco nodded. "Literal god-given powers aren't exactly precedented for us, so we don't have much to work with. Do you have a greater control over salt water versus fresh water?"
"Uh." Percy frowned. He'd never really thought about that. He knew his dad was the god of the seas, but he'd always thought about his gifts as hydrokinesis, with some other added perks on top of it. "Maybe? I don't think so, but there's a chance that's true."
"Something to test." Cisco muttered. "And what about your other powers? Talking to sea life? Being able to summon hurricanes and literally distort the earth?"
"What about them?" Percy shrugged.
"How much do you use them? How powerful are they? How useful are they?" Cisco asked. He glanced over to Caitlin, who was still hunched over a microscope and studying his blood.
"Honestly, they've saved my life a number of times." Percy said. "I don't use them that much, but the way it was explained to me, my Earthshaker and more volatile abilities are connected to my emotions. They've only ever come out when I've lost control of my emotions."
"Hm." Cisco cocked his head and looked toward the ceiling. "Is that the case with your dad as well?"
"Uh… kinda. From what I know, his powers are also connected to his emotions, but I think there were a few times where he could manipulate the Earth without needing to be off his rocker." Percy spitballed.
"Okay." Cisco nodded. "We can work with that. We should try to get to a point where you can access those abilities without needing to be on a rampage. It seems doable."
"We can dive into any mythological texts we can get our hands on." Barry chimed in. "Anything to do with godly powers and how their children's powers relate to them."
"Got it." Percy said. "Sounds good."
"Well." Cailtin let out a huff, kicking her chair away from the microscope and smiling humorously. "I can confidently say that I believe you, and that this makes no sense."
"What do you mean?" Barry's brow furrowed.
"Take a look for yourself, if you want." Cailtin gestured toward the microscope, and subsequently a small sample of his blood. Barry went to lean down towards the microscope and peered through the lens"It shouldn't be possible. I've never seen anything like it."
"What does it look like?" Percy asked curiously.
"It looks like half of your DNA doesn't exist." Barry said, his eyes still glued towards his blood. "Half of the double helix looks normal, but the other half just… isn't there."
Percy blinked. "I don't know what that means."
"We don't either." Caitlin laughed and flung her arms out helplessly. "It shouldn't be possible!"
"Probably best not to question it." Barry said. "If we can't get answers from your blood or DNA, we should probably stick to what's tangible."
"Myths. Fairy tales. Legends. The Iliad." Cisco said blankly.
"Exactly." Barry nodded. "There are probably hundreds if not thousands of descendants of Poseidon. One or two of them had to be at least slightly curious about their abilities."
"But in the meantime, we have you." Cisco nodded towards Percy. The demigod had to fight the urge to look behind him and point at himself to make sure the Hispanic was indeed talking about him. "You've known about these powers since you were 11 years old. We can use your self-progression and awareness of your powers to further your capabilities."
"Sounds simple enough."
"Eh." Cisco shook his hand in a "so-so" gesture. "With Barry, it took years for him to master his own abilities, and even then, I doubt we're even close to maxing out what he can fully do."
"But, to be fair, it's taken a lot of creativity to stretch the power of running fast into throwing lightning bolts and phasing through walls." Barry said. "And we started from scratch with me. You already know quite a bit about what you can do. We're just here to try and give you an extra little push."
"If that extra push can give me anything at all, I'll feel good about this." Percy admitted.
"Well then I like our odds." Barry nodded firmly in encouragement.
"Let's start with your hydrokinetic abilities." Cisco suggested. "I feel like that's the most tangible and easiest thing we can work with. We don't know enough about your other powers for the moment, so we can work on those later once we have a better grasp on them."
"Agreed." Cailtin nodded. "We may not know how demigod abilities work, but we know how water works."
"Exactly," Cisco said. "What do we know about water that you can use to your advantage that you don't already?"
Barry looked towards Percy, "Well, how do you exactly use water? Try to tell us all the ways you've knowingly accessed the element."
"Alright." Percy nodded, cocking his head in thought. There were countless times where he'd broken past the single-minded barrier of only calling upon bodies of water, it was kind of hard to keep track. "Let's see, some of this you already know, but I've created my own personal hurricanes, I've healed my own as well as other people's wounds with water, I've manipulated ice and to some extent snow, I was able to redirect poisonous gasses once, and I can to kinda harden the density of water, or something like that? That's what I did with the water bottle, anyways."
While the three of them took a moment to process everything he'd said, Percy felt a pinch in his ribcage, a beat of his heart that was quicker than usual.
"And… I've controlled someone else's blood before." Percy said. Just saying it made him shiver. Even though his eyes were trained on his hands gripping the desk in front of him, he could feel the other three staring at him. "But I don't wanna do that. Not ever again, under any circumstances."
Unexpectedly, Barry patted him on the back and when Percy looked up, gave him a friendly smile.
"It's okay, man. We all have our demons." From the look in his eyes, he could tell that Barry meant it. Percy recognized the inner turmoil, the almost overwhelming guilt. "Ask anyone in the League, and they'll tell you they have regrets. The important thing is that you learned from that lesson, just like us."
After a pause, Percy nodded firmly, meaningfully.
"So, quick question." Caitlin timidly asked. "Can you control liquids in general, or just the water within it? Can you control melted metals and other liquids that don't contain water, or is it just water?"
"Pretty sure it's just the water I control, and anything mixed into it is just kind of carried along for the ride." Percy shrugged. "But I guess we can test that if you want."
Caitlin nodded in satisfaction right as Cisco perked up a little bit, "Have you ever tried transitioning water between its stages?" Cisco asked after allowing the moment to simmer a bit.
Percy cleared his throat, "Uh, a little bit, but not for any purpose other than making ice for my drinks."
"Never from liquid to gas?"
"Not really."
"I'm sure we can get you there, though." Barry said confidently. He must've sensed Percy's slight confusion in both how he could get there and how it would be useful, because he didn't hesitate in explaining his thought process. "From what you've described, you probably have incredibly precise control over the molecules that make up water, and the amount of practice you've had forcing those molecules to move is why you're so good at creating and maintaining such detailed shapes."
"Okay." Percy said, nodding in a timid understanding and allowing Barry to continue his explanation.
"I could get down to the barebones science of it, but essentially, when you're changing water into ice, you're cooling the water particles and sapping them of their thermal energy. The process of changing a liquid to a gas is the exact opposite. You have to heat the molecules to a temperature where instead of slowing down the particles, you're speeding them up to a speed so fast that they vaporize and become a gas."
"..."
"Basically, liquid to solid means making the water cooler, liquid to gas means making it hotter."
"Got it." Percy nodded. "So, I'm basically just boiling the water?"
"Yup." Barry affirmed. "Think you can do that?"
"Probably, with practice," he answered. "I'm already able to maintain the temperature for drinks that I don't want to get cold. I guess I just didn't realize just exactly what I was doing."
"That's exactly why we're here." Caitlin responded with a smile. "The better you understand how exactly you can do the things that you're doing, the more in tune with your abilities you'll become."
"We should try to get you proficient in changing water between the three states consistently and rapidly." Cisco said. "We can do training sessions to help you better understand how exactly you should manipulate water molecules, but it sounds like if you just practice a lot, you should get pretty good pretty quick."
"I can do that." Percy said. He flexed his right forearm in anticipation, antsy to get started. He hadn't done anything to meaningfully advance the knowledge or potential of his powers in what felt like forever. It was invigorating to feel like he was on the verge of making a mountain of progress.
"You wanna start now?" Barry asked, looking at the watch on his wrist. "I have some time before I have to be back at the precinct. We can go over the basics of this to get you started."
Percy grinned, "Why not?"