This is a release candidate for the Tolrea setting. Thoughts?
Fey are the living embodiment of nature (or possibly just the embodiments of mortal ideas about nature). Nature is fecund, and as a result, fey creatures occasionally breed with mortals; indeed, in many cases the fey are compelled to mate across species lines if they are to mate at all; for example, nymphs and ondine are always female, and satyrs are always male, necessitating that they should if not intermarry, then at least interbreed with mortals or other fey.
In general, when two different kinds of fey mate with one another, the offspring is of the same kind as one of the parents; the offspring of a pixie and a sluagh would have a roughly even chance of taking after either of its parents. Changelings are something different: the outcome of pairing between a fey and a humanoid that does not result in the birth of a new member of the fey parent's kind. Thus, a changeling is the result when an ondine has a dalliance with a mortal man and gives birth to a son, or when a human woman presents her satyr paramour with a new daughter (the female and male children of these fey grow up, respectively to be members of the same kind as their fey parents).
Physically, a changeling usually is a more delicate, refined version of the mortal parent, although changelings born to a halfling or gnome are conspicuously larger than their mortal parent (and they may be similarly oversize compared to their fey parents, if they are the children of a sprite or other smaller faerie). But in most other cases, changelings resemble their mortal parents closely enough to pass as members of the same race if they are not subject to expert examination, and they may even be sought after as romantic partners because of their grace and physical attractiveness.
Also unlike most fey, who grow rapidly to adulthood and then are effectively immortal if they aren't slain by mishap or in war, changelings mature as quickly and live as long as typical members of the mortal parent's race. It's therefore entirely possible for a changeling to pass a lifetime without ever learning that she is not of the same race as her mortal parent, especially if the parent did not realize that his or her lover was a fey in the first place.
Nevertheless, most changelings never truly fit into their parents' societies. Changelings living as elves sleep instead of engaging in revery like their peers, and they do not naturally display the same penchant for swordplay and archery. Those growing up in a dwarven culture may have beards as full and rich as their friends, but they lack darkvision and do not have the instinctive feel for stone and metal that characterizes a true dwarf. Even among humans, a changeling doesn't show the same predilection to pick up new skills and knacks. As a result of their inability to fit in, changelings often gain a reputation as troublemakers, misfits and eccentrics.
Changelings raised among the fey are no better off. Most "pure-blooded" fey look down on their half-mortal brethren, perceiving themselves as superior. In many cases, especially among those fey that hold allegiance to the Unseelie Court, this attitude slides over into outright aggression and maltreatment; a changeling among the sluagh is doomed to be treated as a servant at best. In general, changelings are best accepted among fey kinds, such as dryads, nymphs, and satyrs, that are restricted to a single gender, since interbreeding is a fact of life for them. But even among these fey races, it would be accurate to say that there is a bias in favor of those whose parentage is fey on both sides.
In any case, changeling characters nearly always are outsiders to some degree. If they are naturally charismatic, lucky enough to be born into a cosmopolitan society, and agreeable enough to try to go along to get along, they may be well liked, even admired and respected. But in any society that encourages rigid confirmity, a changeling faces difficulty and ostracism.
Fortunately, changelings are tougher than their appearance suggests. As a rule, they are resistant to injury by conventional weapons that are not forged from cold iron. They are impervious to all magic that affects the mind, which not only protects them from charm and domination spells but also makes it notably harder to use magic to affect their morale or read their intentions, and they even have a weakened version of their fey parents' resistance to magic in general.
Changeling characters possess the following racial traits.
- Fey: changelings belong to the fey type but do not possess the Spirit subtype.
- +2 Dexterity and +2 Charisma. Changelings partake of their fey parents' charm and grace.
- Medium: As Medium creatures, changelings have no special bonuses or penalties due to their size.
- A changeling's base land speed is 30 ft.
- Immunity to mind-affecting spells and effects.
- Low-light vision: A changeling can see twice as far as a human in starlight, moonlight, torchlight, and similar conditions of poor illumination. He retains the ability to distinguish color and detail under these conditions.
- +2 racial bonus on Hide, Listen, Move Silently, and Spot checks.
- Damage reduction 2/cold iron.
- Spell resistance equal to 5 + class levels.
- Automatic Languages: Common plus one other, almost always the mortal parent's native language. Changelings raised by the fey learn Common and Sylvan.
- Bonus Languages: Any, except secret languages such as Druidic.
- Favored Class: Druid.
- Level adjustment: +1.