Most Common Elements: Air and Water. Almost all Slyphs have an Air affinity, and many also have a Water affinity. It is quite common to see cloud Sylphs, and occasionally storm Sylphs!
Other elements are very rare, but not impossible. If a Sylph lacks an Air affinity, they will be flightless, as are many hybrid Sylphs.
Hereditary Magic: Magic is passed down from their parents, as Sylphs are pretty stable and remain fairly uninfluenced by their environment - magic wise at least.
Sylphs can sometimes pick up other affinities from their environment, but their Air affinity will not change. Many Sylphs develop an affinity for Water if raised near large bodies of water. These Sylphs are typically taller than other counterparts.
However, a Sylph raised in a desert is not likely to gain an Earth affinity, nor is a Sylph raised near a volcano likely to develop a Fire affinity.
That's not to say it's impossible, just not very likely. It would probably require generations of Sylphs born and raised in these extreme environments.
Elemental weaknesses/resistances: Sylphs are susceptible to the Earth affinity and its derivatives, but they are neutral to Air affinities, and only mildly susceptible to Fire and Water.
Common locations: Sylphs are often strongly migratory and filled to the brim with the travel bug. They don't tend to stay around in one place for too long, although they often have an area that they are regularly drawn back to! They often refer to this as their nesting place.
Due to this, Sylphs can be found all over the place, and it's not certain where they originated from! There are some Sylphs who annually travel to other continents, so most agree that Sylphs are not native to Owel.
Climate preference: Many Sylphs are fond of mountains and forests, but this is not a hard and fast rule. There are Sylphs who like nesting in the busy Mew York, and others who prefer quieter places like mountain caves.
The only requirement Sylphs seem to have is that they are able to spread their wings freely.
Sentience: Sylphs are sentient, feral Sylphs are either non-existent or extremely rare!
Language: Common. Sylphs are also able to communicate with feral avians.
Trivia: Sylphs are based on the air spirits of the same name, which control and shape the clouds and take care of birds.
These Sylphs take on a similar role as the spirits from myth, as many of them having the Cloud affinity.
Although they do not have complete control over the clouds like their mythological counter part, they can still influence the weather by creating clouds and manipulating them.
They also share a kinship with most all avians, and many Sylphs look after feral avians!
When designing a Sylph, I'd recommend looking at real life birds for inspiration. Sylphs come in all shapes and sizes, some are tall and lanky, while others are short and stocky.
Air/Water Sylphs are typically based on waterfowl, whilst Air Sylphs are based on most other species of bird. The little green one up top is based on an owl, for example.
If you made a Sylph with no Air aspect you'd likely want to draw inspiration from flightless birds.
Sylphs all have a flower near or on the back of their heads. It does not always have to be dead centre, nor does it have to be just one flower. The tall red Sylph has two bluebells hanging from the side of his head!
Sylphs are also able to breed with most all species, much like Flowercats. Unlike Flowercats though, many half breeds are infertile unless they breed with avians. Species that can fly are typically more compatible with Sylphs, however.
Half-breeds can have any affinity, but like with Sylphs, without an Air affinity they become flightless. This is very common in half-breed Sylphs!