By the excellent  Young_Intellegent_Furry_Friend !

Kethrix, "Ruler of Gems"
[KETHend = gem, MaekRIX = ruler]
Nicknames: 'Rix, or IX

DETAILS FOR ART
-Heart is lightly visible
--When experiencing intense emotions, more veins of purple are visible through his body. If veins are visible in his face, he's probably VERY angry... or about to orgasm
-Jewelry may not be the same every day--his kobold gets to pick items from his hoard to dress him in--often none of it even matches (i.e., artists, draw as much or as little as you feel like)
-Floating gems move around and express emotions. They'll be pointing pointy-end towards people who offend him, they might look like they're drooping if he's tired, etc.
-He's beeg! Usually over 14 feet tall, his 'real' size is 7'2", and anywhere above 20 feet he turns into a feral dragon
--(Based on level 20 Giant Barbarian features: up to huge when you rage at level 14 and infinite rages at level 20. He's been changing size for so long that he no longer needs to get angry to do so)
NOTES: no nipples, he doesn't sweat, no post-vore belch-focused art
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THE IMPORTANT STUFF (KINKS)
YES:
-Size difference
--Macro not really
-Cum inflation if the size difference makes sense for it
-Sex: (feel free to ask if not specified or unsure)
--Bi, female preference
---Yes to him domming, or to both chars being equals
----Females domming him is a yes. Not if it's overly demeaning though
----If m/m penetration is involved, he'd be top 99.999% of the time.
-Vore, PRED ONLY, oral vore yes, cockvore maybe
--Digestion yes
---Endo 'yes'--if you can get yourself out. He's more than happy to eat someone who asks, but can't throw up. Bring scrolls of Dimension Door.
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PLACE IN THE WORLD
A curious dragon who seems to have appeared, full-sized, only a few decades ago. Whilst most accounts put him at around 14'4", if a threat significant enough presents itself, he can be much, much bigger--but not taller: LONGER. Any larger than 15' and he seems to go feral, rather literally. Even rarer accounts of people friendly with him say he can be as small, or 'small' as 7'2". Strangely, no accounts exist of him before this time. No stories of an ambitious hatchling or scheming adult of his description appear in records.
A typical encounter for would-be dragon-slayers has them stealth in futile as he's already expecting them, they get a thrashing roughly equivalent to their perceived threat level: local lads trying to impress a lass get a good thump on the head, whereas those adventurers that everyone's been talking about might earn something closer to 'lightly brutalized.' Concussion or bloodloss, they're taking a nap. And then... they wake up. Their wounds are bandaged, and they're lying in a handcart at the side of some road somewhere. They've even got all of their belongings, except--"where's my sword, dammit?" He keeps their weapons.
This process generally repeats at most three times until the offending party either gives up, or apologises. Like some kind of gnomish light-emitting device clicking on in their heads, people eventually realise that they're just fighting a hermit, not a malicious killer, which sort of ruins the excitement of a dragon hunt. He's still not going to give your weapon back, though. Unless maybe it talks too much.
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POWERS
He's got the powers of a D&D sapphire dragon: thunder breath weapon that incapacitates (countered with the Silence spell), teleportation (he's pretty bad at it. His isn't as long as some other gem dragons if you know what I mean), psionic spell-like effects that he never seems to remember to use (hey, if you've got a physique like that you may as well lift things with your brawn, not your brain).
Things he actually remembers to use his psionics for are bending the path of incoming missiles to make him slightly harder to hit, looking fashionable, and saving money on a scabbard.
His floating gems can be arranged as he decides, generally reflecting his mood. He'll be spikier in combat and showier outside of combat. He could theoretically throw his spikes with psionics... but he usually forgets in the heat of combat and just throws them by hand as needed.
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LORE
Why does he keep forgetting about his powers? He wasn't always a dragon, he used to be a kobold, which he DENIES. He's spent the last two decades honing his draconic instincts, thank you very much. As a kobold, he helped slay a sapphire dragon who was plotting to recreate a historic war by manipulating two countries into the same political conditions as the original war--but all that detail went over 'Rix's head. His party pointed and he hit things. When the dragon was dead, he found that its blood was reacting with his own blood, and he became what he is today: a dragon who's really a dragonborn who used to be a kobold. He looks a lot like the dragon that his party slew.
After his transformation, he retired from adventuring with his share of the dragon's hoard, changed his name, found himself a nice cave, and tried to establish himself as a dragon in the area. Just... a dragon with no clout or previous public record. Other dragons generally agree that something's weird about him as a dragon, but he hasn't damaged their reputations or stolen from their hoards, so they don't pay him any mind.
Forgetting to use his psionic powers? He just wants to hit things. Having things hit things without his arm doing the swinging just isn't as satisfying.
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KOBOLD
He's got a single kobold who would defend him with his life and whom he would defend with his life. Generally they aren't interested in eachother sexually, having more of a father/son relationship (though they are NOT related), if 'Rix is pent up enough, he might ask for some favours. His kobold is a fairly powerful sorcerer, specializing in spells that let him move things bigger than he is: (Mage Hand, Bigby's Hand, Telekinesis, etc). During a fight his kobold generally stays hidden and only supports in 'Rix needs it.
His kobold really likes seeing 'Rix fight, to the point where he'll seek out trouble, bring it back to 'Rix's cave and have 'Rix 'save' him.