He for sure would dress him to the nines every day. His cute little mortal will want for nothing now that he’s with him, that’s for certain. Although he could break that silly little ‘contract’ at any time, he has no wish to. He was smitten from the moment he laid eyes on the clumsy beginner mage, and that’s rare for someone like him. Now he simply can’t stop from spoiling him and dressing him in the finest silks and fabrics the demon realm has to offer.

He’s used to dressing himself in jewels and gold, so his precious treasure also gets his fair share. His own golden eyes shine brighter than any dull gem, though. At least to him. Undressing him is almost as exhilarating as seeing him wear those shimmering silks and garments he had made just for him. They’ve grown closer and closer with time and now he can’t help himself but to want to devour him whole, bonded souls sparking as his fangs and tongue dance across flesh.

Hehe sure! 😈

Caelus would, understandably, be flabbergasted and shook, lol. This handsome demon man showing up in his bedroom and grabbing him by the chin, shirtless and decked in jewels, talking about taking him home with him as a PET??? A PET?! He probably blushes and stumbles back and Aventurine just laughs at how helpless he looks. Oh, this beginner level little mage is too adorable. He definitely has to come home with him.

He probably doesn’t give him much of a choice as the portal is closing due to Caelus losing concentration and the ‘familiar’ bonding spell (that he could easily have stopped, but he didn’t bc it’s an excuse to spend more time w/ him) had already been cast! Looks like he’s stuck with him, oops! He’s dragging him into the portal with him before it closed~

Caelus is scared to death obviously but Aventurine assures him he’s safe in his care, and the big castle IS pretty nice. Cae might try and pull the ‘well if I’m your master then take me home!’ But Aven just shrugs and says “You misunderstand. A familiar bonding spell makes the weaker being bound to the other. In this case…YOU are now mine. Sorry, pet. I’ll take good care of you as I do all my treasures.”

Caelus just sitting in his lap on his throne and blushing, face in his hands. What has he gotten himself into? Apparently, the arms of a very powerful and hot (and still shirtless) man.

Oh absolutely! I feel like due to his past of having things taken from him and not being able to have comfort in belongings, a steady home, or even a steady safe family setting, he’s naturally very clingy and greedy with his belongings and things he grows an attachment to. Caelus included.

Even before they might be a couple, he’s subtly watching him interact with other and steers him away from them by ‘popping in’ and convincing him to go on a date with him. When they’re officially together it’s even more so often done. He doesn’t go anywhere with him without an arm around his waist. Everyone should know he’s his and envy him for having him, but that doesn’t mean they can get too chatty!

Lmaooo this is such a funny premise! Room for lots of shenanigans and misunderstandings honestly. xD

Demon King Aventurine coming through the summoning portal, ready to make this mortal suffer only to find a visibly confused, cute little human flipping through his discount spell book and blinking at him with big doe-eyes.

“I was trying to summon like…a little hellhound? A puppy, maybe? Why did I get a whole ass man?” He’s just a silly beginner mage and stumbled over his words. Oh. That’s adorable. Suddenly Aventurine is chuckling and tilting his chin up.

“No need for you to have a pathetic dog. I think this could be interesting enough a mishap for both of us; luck was on our side. It takes raw talent and magical energy to successfully summon me, meaning to or not. Hm…How about you be MY pet, instead?”

It probably like a thing that occurs with how Aven and Ratio canonly meet and start to work together. Aven gets assigned to work with the Guild rep Ratio, bringing along his very curious Stellaron-hosting friend for the ride. (Since they never separate for missions now that he has him privately on his employee list.) Once Ratio realizes that THIS is the Stellaron host he’s heard about, he naturally becomes curious. He sits in on a few experiments on him and is appalled by how the IPC treats him as purely subhuman and animal-like. His respect for how Aven seems to protect him and treat him as an equal grows for this, and he tries his best to be kind to the other during their work time together to show he is not like those researchers that put results above human morale and empathy. (He’s blunt bc it’s Ratio. But I can see him speaking only politely to him and maybe even getting him a snack or something during their mission he saw him eyeing. Consider it a peace offering.)

Aven and Caelus are both hesitant to trust someone of course, but with time he sees how Cae warms up to Ratio and can tell he’s being honest in his politeness and good intentions and has been actively trying to campaign for better treatment of Caelus to the the researchers. Aven had been trying but his influence in the science part of the IPC was minimal. After the hurtful tests suddenly stop and turn much more normal, they know right away it was due to Veritas fighting for it. Caelus gives him a huge hug the next time they see each other for a mission and almost knocks him over, meanwhile Aventurine is grinning ear to ear. “Happy to see you again, doc.”

Ooo IPC Caelus is a really fun idea honestly. I imagine him in this kinda AU as the IPC getting custody of him after he woke up on the Space Station. (Probably handed over by Herta) They probably see him as a walking experiment, doing research on Stellarons using him and also employing his instinctual battle skills for their own devices.

Caelus is sent on dangerous missions as a body guard/guard dog of sorts, and Aventurine felt bad for him from the moment he realized how similar their situations were. Caelus is literally collared with an ‘insurance policy’ neckband that will explode if he ever goes off the rails or the Stellaron loses control. The IPC see him as a dog to use for their own gain. Aventurine is much the same, just a pawn looking for a way out. He sees how they treat him and experiment on him, sees the lethargy after countless tests and pain hidden under golden pools by indifference. He tries to get close to him and let him know he’s not alone, because deep down, he doesn’t want to be either. Maybe one day they’ll turn the tables on their ‘captors’, together?

Caelus would take to the honest empathy like a sponge and suddenly he’s clinging to the Stoneheart and Aventurine insists he’s put on his private list of employees. It takes a lot of gambling and bribing but he manages it, just like he always does when the stakes are high. They watch each others back fully and plan in secret together.

I feel like Aventurine would be very pouty about it and try his best to keep him from meeting him or ‘interfering’ with their friendship/bond. If he somehow slipped through his radar to meet Cae and circle him like prey, teasing him like ‘What does that peacock see in you? You’re so bland and -normal-?’ he would be so pissed. The rare time you see Aven break his act of nonchalant and have that glare of irritation and protectiveness about him.

“Keep wondering, and go back to whatever hole you snuck out of.” Getting in between them and blocking his view of Cae. I bet he’s mostly worried he’d tell the IPC they could get ahold of Cae and use him pretty easily, or something. Of course Aven won’t allow that.

Caelus meanwhile is just surprised by the protective side the stoneheart has and naturally is suspicious of Sugulite after his ‘friend’ tells him to stay away from him. He trusts his judgement. Later he has to deal with a very clingy and pouty Aven. (I’m the only gem you need right? Sob sob 🥺)

Oh yeah he would definitely be suspicious and hard to open up, as usual. Cae is gonna have to use his head and try and work around this, as Aven is a master at reading people and their intentions. But like you suggested, he’s very honest to a fault and can’t hide his passion for helping him and harbored affection and I think Aven will sense that and just be confused if anything! Eventually he eases into the role and is like oh…Okay. He genuinely just is on my side. That’s. Something.

When he catches feelings it is HARD and all at once and he doesn’t know what to do with all the attention and knowledge of his likes and dislikes and things. Like Cae already has such an advantage! Even if he doesn’t fully know that, he can tell it in the little ways he does things for him and treats him. He absolutely has to return the favor with deep loyalty and love. He wants to learn everything about him and make him happy, too. Whatever made Cae want to save him and help him so much he might never know, but he doesn’t mind as long as he gets to see his smiling face every day.

I’m not super familiar with the isekai genre but I imagine Caelus would fit better in the role since he’s a natural protagonist!

I’m imagining a storyline where Caelus has been playing a popular video game and got really invested in a character (Aventurine) and his wish to help him lead a better and happier life got granted by him getting hit by a truck and plopped directly into the game itself! And now he’s on a mission to stop him from getting hurt or worse in the storyline but also trying not to let it slip he’s not from their world & knows wayyyy too much about everyone. He’d def put himself right in the drama because damn it if he’s gonna get this chance he’s going to take it!!

For AvenCae:
Aventurine has trouble sleeping a lot, but ever since he started being able to sleep with Caelus at his side he sleeps a lot easier. Caelus wraps around him like a koala, legs thrown around his waist and arms around his neck. How can he not sleep soundly with his star so close he can feel his heartbeat? Now they both can tell they’re safe all through the night…When it rains Caelus is quick to wake up and instantly is even more cuddly, insisting on staying awake until Aven falls asleep first. He’s protective of him when he shows that rare weakness the rain brings out in him and will bring him a warm drink and nuzzle his neck.

Aventurine is very keen on reading moods and expressions due to years of faking his own and doing business, so he can always tell when Caelus is getting in his head or overthinking something. He’s quick to spoil him with treats and hugs him from behind, hand feeding him food and trying his best to distract him. He knows what it’s like to be overcome with thoughts you can’t escape. (I feel like Caelus probably has PTSD from some of his near-death moments and battles…That’s scary stuff.)

For TioCae:
With Ratio, he’s very much the big spoon and like to tuck Caelus in under his arm and into his side. He gets stuffy if he’s all on top of him but won’t wake him up even if he can’t sleep and is uncomfortable. He’s a softy for Cae’s sleeping face and wouldn’t dare wake him when he’s cuddled up to him and sleeping so soundly. When Caelus is rolling around and pulling off the covers he WILL pick him up and readjust him though or he would end up in the floor. 😅 Caelus is a deep sleeper.

Ratio is very aware Caelus sees himself as a tool to be used and help others a lot, as seen by his self-sacrificing nature. It’s a way for him to feel human and useful, to distract from the Stellaron and his unsure past. He is also familiar with feeling inadequate due to his failure to reach the Genius Society or Nous’s eye, but he thinks Caelus is OUTSTANDING if anything. So he will often stop him from going out to do some dumb quest by asking for his assistance with something instead. He doesn’t ask for help often so of course Cae is quick to agree to help his bf instead of a random person who needed a dumb quest done. (Ratio can’t just admit he wants to spend more time with him + keep him from being used so much.) On Cae’s side, he sees Ratio overworking and he will literally worm his way into his lap at the desk and force him to get up and take them both to tuck into bed. ☺️ Clingy raccoon wins~ He will be extra cute and cuddly just to keep him from thinking about work anymore and rest.

Ahh well going off what I picture in my head, I think they may have twins first. A little girl and a little boy~ The boy looks a lot like Kakavasha when he was younger but has silver hair and Avgin eyes~ The little girl has long pretty blonde hair like her father and Cae’s golden bright eyes~ Their fins would be very pretty and flowy to match the mix of both their parents, with lots of iridescent scales. I think the daughter would take after Aven and have mostly purple/blue while the son would have the silver and gold tones.

🔞Hehe, me too tho — /also slapped
I was reading merfolk courtship lore and stories while writing Seafoam and like to imagine the process myself. First and foremost is of course courting! Lots of gifts and doing things for his Cae to try and show he’s a capable mate that can provide. Then, of course, was the mating bite and claiming him, also part of the process. For mating with a human, this process would be what turned him into a merfolk as well after successfully being filled and plugged long enough for the magical properties of his cum to do their thing. 😘

I imagine after his body fully adjusts and gets used to his changes, he would go into a heat cycle in reaction to being mated and claimed already. Merfolk mate for life, and often die of sadness if their mate passes, so their bodies and hormones/pheromones are all very entwined with each other and their mate. It helps them tell what the other is feeling, thinking, and what they need without even having to voice it. Vasha would sense him going into heat and usher him into their cave and keep him there while they prepare the nest and den for future pups. During heat it’s pretty understandable they’ll be inseparable so he would forage and prepare a food stash and supplies before enclosing their cave for safety & breeding time ~ During peak heat hours they will mate as many times as possible to ensure its successful and Caelus will be absolutely spoiled throughout all of it. (Hand feeding, cleaning, anything he needs and more. And of course taking care of his heat symptoms in any and all ways he needs~) Even though Aven is very passionate and enthusiastic/ lost to his love and instincts he is still very obsessed with making sure his beloved is unharmed and wants to bear his pups. He’s still new to mer life and so small…Will it be okay? After he gets the go ahead though he was like an excited dog given a bone and couldn’t be pried from his lover’s body for hours. Filled over and over and forced to keep it all inside as much as possible by cock warming in between. He doesn’t want to be apart from him for even a second until he is fucked so full of his seed he can’t take another drop.

Cae’s chest will swell with milk and so will his stomach with his pups after the very successful breeding and Vasha will somehow becomes even MORE protective and passionate about spoiling and caring for him. Like the treasure he is 🥰

I imagine Caelus’s merfolk form would be silver and gold, maybe with koi fish-like patches of gold on silver. Flowy tail like a fancy goldfish too <3

Adjusting to his new form and life was challenging! Kakavasha had to help him learn to swim with his new tail in the tide pools for a while before they could venture off and return to the deep sea. He’s still a little clumsy but Vasha finds it adorable and swims slow for him to keep up, holding hands to stay together. Caelus is so, so curious and awestruck by the world under the ocean. He’s been stuck on that island so long he never thought he would see such beautiful sights and wonders. They made a home together in a pretty coral covered cave where they and their future family will be safe and happy. 🫶

Caelus probably tries to befriend and play with a lot of sea life but Vasha is protective and jealous when he sees him admiring a fish’s scales and fins. (Mine are prettier! So praise me instead! 😖) Then Caelus just laughs & lets him wrap his arms around him for a kiss and nuzzle. Vasha still does most of the hunting because he LOVES spoiling his beautiful mate with gifts and bc Cae is inexperienced. But he’s okay with it~ He loves doing things for him and half the cave is full of shiny shells and treasure just for his precious treasure ❤️

This scenario has so much room for softness and vulnerability. 🥰 Caelus is so overwhelmed by his heat and what to do, and Aventurine has plenty of experience keeping his own heats under wraps and staying safe. He would usher Cae into a safe room / apartment together like a mother hen, comforting him the whole time and scenting him to calm him down. Did no one really teach him? It makes him angry but for right now, he has his sweet star to take care of.

Controlling his own needs and hormones will be hard seeing Caelus so vulnerable and soft (might even trigger his own heat if he's not careful, he's just too adorable aaa), all curled up in a nest they built together of his expensive clothes and bedding. He'll coo to him the whole time, taking the initiative to help them both cool off and covering him in kisses. His body is so hot and feels like its glowing with the Stellaron inside. He'll assure him he'll take care of everything, no need to stress his love any more. Just relax and let him handle it, cover him in love and soft markings.

He understands his anxieties and fears deeply from past worries of his own, and Aventurine isn't exactly the most used to being vulnerable with others. Not anymore. But, right now, with nothing but him and Caelus and a soft, perfect nest...He can let his inhibitions and fears of intimacy go. His hand is always on him the whole time, if not carding through sweaty locks then holding his own tightly or draped over his hip.

Aventurine would growl and hiss at any Alpha or trespasser for sure. No one is going to take a step towards their den on his watch.

I feel like Aven would be the type of yan that is protective as HELLLL. He would want Caelus safe and kept by his side as often as possible, and when he must be away from him he’ll have him tucked away in a luxury apartment somewhere with a lot of security efforts. He wants to keep him to himself and protect him from all those who would want to hurt or use him; he’s his little sunshine only. But he also can’t help but want to show him off…! So he will take him with him all over and hold him by the waist the whole time so everyone knows he belongs with him. And then when they get to looking too much, he will dig his fingers in and possessively make him weak in the knees in front of them with a quick sloppy French kiss. They can all watch, but no one can touch what’s his and his alone. He’s tired of the world taking everything he loves from him, so he won’t let it happen again! He probably rushes him back to their shared apartment and doesn’t let him leave the bed for hours. 🤭

Ooo what a cool idea! I feel like a tripe Alpha sandwhich like that would include a ton of roughhousing and messy mating. Part of Caelus wants to fight back and let his inner Alpha out, but the teeth chomped into his throat make him moan and submit by instinct. Inwardly, he loves it. The conflicting instincts make him more sensitive and horny than ever and once he’s had a taste he can’t help but want more. His Alpha side will manifest in being greedy and growling and TAKING more from them in return for his submission. Aeons know if he can but he WILL try to take both of their knots.