Taken from an essay by Prof. Gideon Ulf, Changeling scientist.
As a changeling gremlin, I have always been fascinated by the existence of our kind. Which has led me to explore the way we are born and the diversity of our beings.
If you've read faery lore, you've heard of the changelings, human babies who have been replaced by the fae. The truth is not too far from it. Now, before you worry about your children being taken away, know this; Fae do not abduct children, the process of creating a changeling is not dangerous.
You see, changelings aren't impostors so much as two spirited being. They appear occasionally when a fetus or newborn is dying. The spirit then join with the child as to keep both of them alive. The child is revitalized by the spirit's energy while the spirit will be able to feed (harmlessly) off the child's essence to keep it alive later in life.
Once that is done, the changeling will live normally with his spiritual nature awakening from time to time and sometimes they will even 'bloom' into full fae. But this is quite rare. Of all changelings, maybe 2 percent actually do so. Most live relatively normal life, often as artists or activists.
There are three kind of changelings that exist; The Fair ones, the Wild ones and the Lost ones. They are the three types of spirit that can merge with a child.
The Fair ones
The fair ones, are the traditional changelings, children with the spirit of a fae inside of them. Their attitude is determined by their fae heritage, Recaps tend to be intimidating and greedy, Sidhe tend to be vain yet passionate, satyrs tend to be easy going and so on.
The Wild ones
Much rarer than the fair ones, the wild ones are children with the spirit of an animal in them. Their personalities corresponds to the spiritual trait of their totem. Although they do not posses the same supernatural powers that Fae changelings do, they are able to communicate with animals in the same class as their totem such as birds, snakes, canines.
The Lost ones
Even much rarer than the previous two are the lost ones. These are the union of conceptual spirits with flesh. Their name comes from the fact that these spirits posses no concept of living and being.
Often, the child develops mental problems and are disconnected with reality. They often ends up in mental hospitals, diagnosed with schizophrenia, autism, multiple personalities, fugue states and many more. Some do manage to adjust to society, but generally only with outside help.
Of all types of changelings, they are also the most powerful, possessing much of the abilities of their "Parent" and a lack of need to feed upon energy sources. They however tend to not know their own abilities.