Dragon

Dragons used to be a normal species, until the same thing happened to them as it did to Humans. One of this species of massive predators came in contact with souls and gained many souls instead of the humans who gained a type of enhanced consciousness they gained Godhood instead. Not only was this first "true dragon" a god, but a powerful one at that and with that power they transcended the weakness they saw in their species, before they were merely another species of large predator, however with magical changes applied to their species the dragons became something else.
The first draconic god, gave the dragons wings, to rule the sky too like so many others of their lower ancestors already did.
They were given powerful magic over an element, they were given control over a couple different ones and had their bodies changed based on which one.
The dragons were also given the ability to shapechange, the less skilled ones would have a couple forms while the skilled ones could transform into whatever creature they wanted.
The last gift of their first god was to transcend biology, The dragons could have children with any species and create partially draconic offspring. What’s more is that the offspring could through intense focus and practice trains their draconic abilities and eventually become just as much full dragon as their draconic parent, this could even happen with a heritage further removed from a dragon, though the further away you are the harder it is. Draconic transformation is its own article.
Dragons can still also be born as full dragons from 2 dragons, the issue with that is that female dragons lay VERY few eggs and it's a momentous occurrence.
Through their magic dragons are able to have children with other species. children which have partial dragon in their blood, can have a Draconic transformation, this is a magic that is written into the biology of dragons that allows the dragon features of a partial dragon to "grow" becoming more and more dragon and unlocking more draconic magic.