Fey

The fey are creatures of extraplanar origin. While fey creatures can exist on our plane, the First World (ancestral home to the elven races, including the Shadar-kai) is their true home.

Fey on the Material Plane

Some fey creatures that live here may have been exiled or cast out from their original home, for reasons unknown to us.

The link between the elves and the fey is still mysterious - perhaps the elves are descended from the fey, or are themselves fey, though this is debated. Elven traditions speak of them coming from an ancient 'woodland home', and being expelled from it long ago. Some elves, particularly the Austvagoy in the north, believe that their dead return there and exist as ancestral spirits whom they can contact. This may also be true of fey creatures, although we don't know enough about them to be sure.

The fey don't worship any deities that we know of and some scholars speculate that they do not have souls, and therefore are cut off from the divine.

There are gates to the First World, powerful artifacts? entities? called the Irminsul. They take the form of massive, ancient trees. The wood is considered very useful for creating magic items or casting powerful spells, and so many have been destroyed over the years. It's very likely that there was one at Seda Grove.

Certain types of fey are powerfully linked to trees - dryads and hamadryads in particular. Hamadryads are the more powerful of them, bonded to entire forests, and do not necessarily die when their trees are cut down or they are separated from their forest - although it can enrage them or drive them mad.

Dryads are weaker, linked to a specific tree, and will typically die if their tree is destroyed, although the power of a hamadryad can aid them to bond to a new tree and survive.

Angels in disguise

When Serpent was imprisoned, and the gods of the Wheel came to power, the angels were nearly wiped out. Some escaped and survived by taking on other natures. Some became demons. Some became the djinn. Some may have become fey. They likely retain their memories of what they were before. But in order to blend in, they will have had to truly become whatever they were attempting to imitate.