A Changeling is a half-faerie. They are always half-faerie and half of a non-fae race. They appear to be of the non-fae race, the only notable change due to the Fae parent is that their height will be raised or lowered, but remain within the races normal range.
A Changeling has a ‘lifespan’ equal to that of an elves, by which point they must have chosen to either become a full Faerie or become a (insert race here), hence the name ‘changeling’. Until such a time they age at a normal human rate until the age of 18, after which their aging stops for a period before resuming at a decelerated rate. As such, a changeling will, after the age of 18, always appear to be an adult or older. If a Changeling doesn’t pick to become either (non-fae race) or Fae, then after the age of 135 they start progressing look-wise at a rate of 1 human year every 7.5 years. By the age of 750 the Changeling will die, possibly of natural causes.
If the Changeling chooses to be human they must determine what their current look-wise age would be, and this is what age they are considered as a human. They then progress at a normal human rate. (using the proportion <age-of-changeling>/750 = <tbd>/100)
If they choose to be a Faerie, their looks, size, weight, and racial characteristics all change to that of the Fae they were born from. All Fae are semi-immortal, never dying of natural causes.
Note that there are, in fact, certain types of Fae within the below categories that absolutely and irrevocably should be considered evil, though none are guaranteed to be good. Also note that, while that certainly is the case, some of these are evil in ways that seem strange, and maybe more towards a neutral standing than out-right evil. These and other specifics will be specified within the Faerie type page specific to that particular Faerie. Also note that Changelings can tell a direct lie, unlike most Fae.
The Changeling can be human and half of any Fae category, which are listed below.