Changelings are classified under the Shapeshifters and are Unseelie Fae. They are the most gifted kind under the shapeshifters and have the power to copy about every form. They can only copy each kind once though and therefore have to choose one look in which they will shift into again and again when taking the form of that respective kind.
Changelings are widely feared due to the fact that they grow up very close to normal mortals without them even noticing it. When no host family is available, changelings have even been seen killing the offspring of a family and making their own look like the dead one, so that their child is raised by the family without them knowing that their real child is dead. Most of the time, changelings simply lay down their offspring on doorsteps or place them where they are bound to be found. Of course, they disguise the offspring as the species of the host family.
Almost every changeling grows up without even knowing what they are. Another reason why they are feared is because they are said to bring bad luck, so a very unlucky family, that has had only good fortune before, might recognise the changeling as such due to such circumstances. Another easy way to expose a changeling is by their unusual ageing. A changeling ages only half as fast as a normal child [note to people who want to create a changeling: they age the same as a human ages] and therefore are easily kept apart from normal children. But since also this is sometimes seen with normal children, due to mental illnesses or the like, there is also another way to expose a changeling. To play them music. All fae creatures have a love for sweet melodies and therefore will respond more actively as usual children to music.
If by chance, the changeling is not exposed by the age of 13 to 15, then it will become very clear then. This is the age when the changeling matures. They have been raised by the host family and now are physically considered an adult, so their disguise starts to falter. Most changelings are shocked about the changes and will react with panic since they have believed their look until then to be their real body.
At first, it starts rather harmlessly with a growth spurt. They will grow to a, for their kind, very large size. Equine changelings, for example, have been seen to grow to about two meters of size, measured at the withers.
After the growth spurt, the changeling’s eyes will start to change from their mortal looking eyes to different coloured ones. After the colour changed, they will start to glow and at last, the pupil will change from a round to a slit-shaped one. The change of the eyes is gradual and takes several days so that certain features will start to appear more and more until they are not recognisable as the previous eyes anymore.
The next step is the horns that will grow between the ears. They are usually quite small like those of a young goat. The growth of the horns takes a few weeks.
When the horns are fully grown, the coat/skin/feathers/scales colour will start to change to black [all changelings are black in their natural form] gradually. If the coat/skin/feathers/scales is/are already black, then the only way to notice this change would be the disappearance of any kind of markings. At this stage, they will also grow sensitive to iron, since their “mortal” skin has so far protected them from it.
The following changes depend on the kind the changeling is and how their natural form looks like. The most reported cases are of equine changelings that also have taken an equine form as a disguise. For them, their ears would get thinner and longer with pointed tips and a strange tuft of hair at the back of the ear. After that, the tail will become like a lion’s tail. Long and slightly furred, with a tuft of longer hair at the end of it. This tuft is usually the leftover of the “old” tail they wore while in disguise. Afterwards, their legs will be getting longer as well and end in split hooves, like those of a deer.
As the last stage, no matter which kind’s appearance they took, the teeth will change to solely sharp ones, like those of a reptile and males will even get stings on their back. The stings are said to add to the mimicry effect of their look since a changeling is most vulnerable in its natural form and therefore looks dangerous to protect itself.
The total change from the disguise to their natural changeling form is said to take about two to three moons. Usually, the changeling is even exposed before completing their unwilling transformation and then chased out of the house. Not rarely, changelings are even killed.
The change from a loving family to one that hates the changeling, will often cause them to hate in return so that they follow their Unseelie nature and turn against mortals. Most changelings just mock them, but others might even resort to killing them.
Once a changeling has completed their transformation from the disguise to their real form, they can from then on change their appearance at will. At first, they will only be able to change back into the form that they have worn so far and as which they have been raised, but with time they will also figure out how to transform into other species. The more a changeling can visualise the form they are transforming into, the better they are at shapeshifting. Some very creative and talented minds even succeed to transform into imaginary forms.
A changeling has not the need to eat. While they have organs to digest food and therefore physically can eat, they do not need it to stay alive. The only things they need are water and air.
There are no such things as half-changelings. A changeling can reproduce with a changeling, as well with a mortal. For that, they have to take a mortal’s form though and the offspring would therefore also be mortal and not a changeling. Only two changelings can have a changeling as an offspring. Changelings are loners, though, so they do not care for their young. In the first moon after birth, the mother has the ability to change her child’s appearance at will and with that builds their disguise. She then places her offspring so, that a possible host family can find them and raise them.
This act might seem cold-hearted to mortals, but it just does not lie in a changeling’s nature to care for their own young. It sometimes is seen that changelings care for the young of others. Orphans, who do not have anyone anymore, so the ability to care for another creature is still existent, due to being raised with mortal morals. But the bond between mother and child cannot be built at all.
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This species is based on the mythological creature with the same name from Celtic mythology but was developed in a direction that does not line up with most mythological stories anymore. Therefore, if you search for mythological information of changelings, then don’t use this as a reference, since it is the artist’s own interpretation of what a changeling is.