For this reason, a Changeling will usually choose to take the form of a race with red blood. A close observer may notice that a Changeling's blood tends to run a bit thinner than most other races. Oddly enough, changelings have no bones. Instead, their skeletons are made entirely of cartilage (the same as some fish).
No. This answer isn't immediately obvious reading the text of Shapechanger, so it's worth going through point by point. First, the changeling's "true form" is humanoid, has flesh, and is not a skeleton.
While changelings can look like anyone, they do have a true form. Their natural look can be scary to some due to their lack of detail and distinctive features. Their skin tone is always pale, either white or light gray, and they tend to have slender bodies with limbs slightly longer in proportion to other humanoids.
The true form of a changeling is a bit paler than a typical human with slightly elongated limbs. Their eyes are colorless and ringed by black as pictured in the artwork above by Julia Zhuravleva. They have no body hair, but the hair on their head can be platinum, white, or silver.
Changelings born from two changeling parents are born in their natural form: pale, slender, with colorless eyes and white hair.
A common way that a changeling could identify itself is through displaying unusual behaviour when it thinks it is alone, such as jumping about, dancing or playing an instrument – though this last example is found only within Irish and Scottish legend.
Changeling Reproduction
If a changeling with the Racial Emulation feat matches its subtype to that of a partner, a child resulting from the union will always be of that humanoid subtype. If a changeling in a female form conceives a child, she loses the ability to change her gender until after the child is born.
Changelings have red blood like a majority of the other races. Bleeding around others may alert many that the Changeling is not of the same race (should the blood color vary). For this reason, a Changeling will usually choose to take the form of a race with red blood.
Changelings are largely equine in appearance but possess insect-like characteristics. Originally, they had black carapace-like coats, webbed manes and tails, blue reflection-less eyes (unlike their queen's), fangs, bent horns, jagged ears, insect-like wings, and holes in their legs.
Obviously, a changeling's appearance can change at any moment, but they do have a true form. Their true skin is usually grey or pale white, and their facial features are blank slates to an unnerving degree. They're typically thin and gaunt, and their hair is usually silvery with an occasional green or pink tint.
A changeling can make it LOOK like they have sharper teeth or claws, but this doesn't actually give them natural weapons; it's a deception. Essentially, it is a form of disguise self, NOT alter self.
Within this description there are variants of changelings that show subtle differences. Some have opalescence in their skin (as if it contains various colors instead of just being white) and their eyes can be completely black.
Changelings are humanoid creatures with discolored, slimy skin, hollow eyes, and a round mouth with many teeth. They can appear human, but their true nature is revealed in their reflection.
Some attributes might give away the identity of a Changeling. The child left in place by the fairies may have red eyes and voracious appetites, losing their tempers if neglected for a moment. Disruptive children were sometimes called Changelings and kept in isolation.
A changeling can't make the wings at all. If they had wings, like from a class feature or something, then they could look like an Aaracokra with wings because they will have those limbs at that point.
Most changelings don't know they're changelings.
Though they may always feel somewhat different or removed from human life, most changelings are too young to understand who they truly are.
Changelings typically have large eyes with narrow pupils, ranging in color from white, to yellow, to black. Hair colors are similar: Light grey, platinum blonde, shades of silver, all the way to the darkest hair color being a light brown.
Even when in humanoid form, Changelings did not need to take in sustenance. Odo noted that he once attempted to eat after assuming humanoid form for the first time, but found the experience not only unsatisfying due to his lack of taste buds, but "messy" for reasons he chose not to elaborate.
You can appear as a member of another humanoid race which will include things like tails, frills, gills, wings, horns, etc. However, your stats do not change so you cannot use the tail prehensively, cannot breathe underwater with the gills and cannot fly with the wings.
Although they're not affected by sunlight at all, a Changeling's most common weakness are Gaggletacks (horseshoes made of pure iron), which reveals a changeling's true nature through physical contact of anywhere on the body.
Changelings have the unique ability to transform their body to look however they want, provided they keep the same arrangement of limbs they already possess. It is very rare to actually see a changeling in it's 'true' appearance. Even when disguised, changelings can instinctively recognize each other.
Will a legless changeling regrow both legs when it copies someone? I say no. The changeling can change their coloration, hair length, sex, height, and weight, but they can't change their number, arrangement, or function of their limbs, because nothing in the feature says they can or even hints at it.
Changelings are typically born with female anatomy, but some prefer to maintain male primary and secondary sex characteristics once in control of this ability.
A mate to a changeling can be of any race; there are several examples of changelings being mated to humans, other changeling breeds and even Psy.
Age. Changelings mature slightly faster than humans but share a similar lifespan—typically a century or less. While a changeling can transform to conceal their age, the effects of aging affect them similarly to humans.