My try at making a good creature story, I don't own HP.

***Prologue***

It was not common knowledge that the Potters had Veela blood in their line as well as several different types of Elven blood, but it was true. No one could be sure what creature inheritance would manifest in their children or whether their child would be a dominant or a submissive.
Although one couldn't be sure, there were some signs that pointed towards what they would become on their sixteenth birthday. Harry didn't know that creature blood could be found in his family or what signs to look for.
It was for this reason that he did not take certain precautions to protect himself and others from the creature that would manifest in him.
As Harry got called to the living room a month before his eleventh birthday he didn't have any idea that the first major attribute of his creature nature would present itself. As he walked in, his head low and his eyes focused on his toes, just the way that he had been taught, he missed the look from his Uncle Vernon.
If he had been looking at Vernon he would have noticed the look on his face morph from disgust to burning lust, his eyes darkening. Before Harry made it more than a few feet into the room he felt himself shoved into the wall face first, with his uncle at his back. He tried to pull away only to get his face smashed into the wall further, and his pants ripped off.

***A MONTH AND A HALF LATER AT GRINGOTT'S***
Griphook was the goblin assigned to the Potter vaults and as such when Harry visited Gringott's for the first time, he was the one to bring him to the main vault to withdraw money for his supplies and other necessities. As Griphook had been the Potter vaults' goblin for many generations, he was one of the few that knew every Potter had some form of creature inheritance, so whilst Harry was gathering money, Griphook collected a few books and different heirlooms he may need for each possible inheritance.
When Harry arrived at the room he would be staying at until the first of September he took out the bag Griphook had given him and read the note it included,

Young Master Potter,
I have gathered together things that may prove themselves useful to you.
Please read through the passages contained in the first book until you find
the passage which sounds like the symptoms you are exhibiting.
Then read through the passages in the other books to learn how to control
these behaviors. It is vital you do this. It may come as a shock, but the Potters have creature blood running through their veins, and as such, so do you. You are beginning to receive your creature inheritance and must take these precautions to protect yourself and those
around you.
Griphook

Harry read over the note quite a few times before deciding that yes, the note did indeed say that not only was he a wizard but he was a creature as well. He hoped the books would help him realize what that meant.
After setting the note aside he picked up the first book 'Potter Creature Inheritances' and began reading on the first page. As he read through each creature description he could only find a growing list of what he was not, this list included Blood Elf, Water Nymph, Dark Elf, and Fire Nymph, along with various other types of elves, nymphs, and fae.
He thought he had found his creature as he read through the section on Veela, until he read that they preferred exotic foods and meat, he preferred plain fruits and vegetables. So adding that possibility to the seemingly never ending list of creatures that he was not he started reading the very last passage in the book.

CYGNE VULPES
Cygne Vulpes are cousins to Veelas. Like Veelas they are very beautiful creatures. Unlike Veelas however they are mostly male. Cygne Vulpes are a race of magical humanoids. Like Sirens of Greece they call men and women to them with their beauty and voices. Hearing the voice of a Cygne Vulpes, like that of a Veela, can cause people to do anything to please and impress the Cygne Vulpes, even endangering their own life in the process. Whereas all Veela can grow wings only dominant Cygne Vulpes can.
A Cygne Vulpes will not know their sexual preference until they meet
their destined mate or mates. However it is extremely rare for a Cygne Vulpes that has multiple mates to have more than one of those mates be another Cygne Vulpe.
Submissive Cynge Vulpes are able to turn into foxes after
their eleventh birthday and grow fox ears on their sixteenth whereas
dominant Cygne Vulpes can transform into swans after their eleventh birthday. For this reason they are often confused with their close relatives
Nekos.
If they do not take the necessary precautions, a Cygne Vulpes' allure
can affect anyone that is not in their direct bloodline (the Potter
Bloodline for us). The allure can affect anyone even if there was only hatred before.
Submissive Cygne Vulpes are one of the only male creatures
that can get pregnant by someone who is not their mate. All Cygne Vulpes have the eye color of the gem they must wear to control their allure, this is because each jewel's chemical build works with each Cygne Vulpes' magic.
Only once a Cygne Vulpes has mated with a Cygne Vulpe with a different eye color may they wear a different type of gem, and even then, only the jewel of their mate.
Submissive Cygne Vulpes eat mostly fruits and vegetables unless they are pregnant, in which case they will eat only what their dominant puts in front of them to eat.
Without precautions including wearing something that contains their gem, a Cygne Vulpes' allure can cause people to do anything to have the Cygne Vulpe even if that means by force.

That was it, he was a Cygne Vulpe, with the facts he had been given, everything fit. So that meant that he could turn into a fox or a swan. That also meant that he had an unknown amount of unknown gendered mates, it was all confusing for Harry…
After pondering on the thought for a while he went through the other couple books and found that Cygne Vulpes could use elemental magic as well as normal magic, and also that once he had a personalized item with his jewel it would help harness and control his powers.
Though his family heirloom with an emerald would not harness his power it would help to control the allure, so he slipped on the necklace before heading down to get a bowl of fruit salad.

***TIME SKIP: SEPTEMBER FIRST***
Harry had been practicing and could turn from a human to a fox most times but still had some troubles turning back at will. An older woman who had introduced herself as 'Professor McGonagall' had previously left him and all the other first years' alone on the staircase, as she got ready for the sorting.
Harry could only focus on one first year though and as if reading his mind the blond walked over, "the name's Malfoy, Draco Malfoy."
"Harry Potter." he whispered with his head bowed.
"I can help you choose the right sort of people to associate with." Draco said holding out his hand. Without even thinking about what was said Harry took the offered hand surprising everyone around them.
As the door opened it made Harry grip slightly tighter before dropping his hand. Professor McGonagall then led them all into a room she the Great Hall explaining that they would each be sorted into one of four houses; Gryffindor, Slytherin, Ravenclaw, or Hufflepuff by something called a sorting hat.

Harry didn't really pay attention until he heard the name Draco Malfoy, then he watched as he got sorted into Slytherin and walked over to the Slytherin table.
Soon enough he heard "Harry Potter." And so he walked up slowly to the stool, sitting on it as the sorting hat got placed on his head. As the hat began talking all he could think about was the blond boy who had just been sorted into Slytherin.
Finally the hat broke through his thoughts "So it's Slytherin you want huh?"
Then to the whole room "It has to be SLYTHERIN!" The whole room went quiet until he stood up removing the hat and the Slytherins began to applaud. He walked over silently with his head bowed and sat in the spot Draco made sure was vacated.

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