So you want to play a half-breed?

Who and What Are they?

A majority of Scarterrans are of mixed elemental ethnicity. You character can be almost any mix of elemental heritage, even a relatively rare combination like Fire ethnicity and Air Ethnicity.
You can also play a character with multiple national ethnicities. Sometimes people conceive children across national lines. There is no reason you cannot play a dwarf who is half-Stahlheimer and half-Meckelorner dwarf. It might be a minor scandal among traditionalist dwarves but at the end of the day, such a person is just a dwarf. Humans and elves have enough trouble telling Meckelorners and Stahlheimers apart anyway. At the time of this writing, I have twelve separate gnome ethnicities and 13 human ethnicities written out plus another six or seven in my head canon. They can and do mix. You can make interesting story hooks based on your character's mixed heritage without playing an actual half-breed.
What I mean here is half-human half-elves, half-orcs, Gnome-human hybrids, Elf-gnome hybrids, and Man-dwarves among other mixes of two species though most Scarterrans use the term "race" and not not "species".
Regardless of what type of half-breed you want to play, you need to figure out how your character came to be and how they were raised.
A half-breed character is going to be the sexual result of either an unconventional relationship, a casual fling, or a non-consensual encounter.
Parents with an unconventional relationship is not required for a half-breed to be well versed in both parent cultures but it helps. Also, just because the parents tried to make their relationship work doesn't mean they were successful and stayed together till your character reached the age of majority.
If your half-breed is the result of a casual fling or non-consensual encounter, your character was probably raised by your character's mother and your character likely grew up with daddy issues.
Regardless of how a half-breed was conceived, it is fairly common for such children to be dumped off on a relative other than their biological parents or left as a basket baby. The Lanterns of Zarthus have a code to accept all basket babies, and to treat all half-breeds with compassion, but they are hardly the only place a basket baby (or an orphan or abandoned child) can be left.
If your character was a basket baby, your character might not know who his/her biological parents are and probably grew up alone or bitter or found a non-conventional surrogate family.

In Scarterra, there are more half-human half-elves half-breeds than all other half-breeds combined. Largely because most other hybrids are sterile, hence why they are sometimes derogatorily called "mules". Most so-called mules are so rare that even a well-traveled Scarterran adventurer can travel thousands of miles and never meet one. Most Scarterrans that are even moderately well traveled and/or live near a crossroads have met a few half-elves. I'll cover the mules first.

So you want to play a Mule Race?

The nickname "mule" implies that these half-breeds are discriminated against and to an extent this is true, but on the whole a character like this is going to be an object of curiosity and fascination more often than an object of derision and hatred.
There might be localized concentrations of hybrids somewhere but in most cases your character is going to be the only one of his/her kind for a 100+ miles in any direction. Characters like this either learn to become loners or they will latch on to the identity of their religious, political, or mercantile organization for their sense of belonging. A lot of these characters use a cosmopolitan adventuring party as their surrogate family.

Now into the weeds!

Macro Photography of Green Grass by icon0.com

So you want to play a half-orc?

In Scarterra, half-orcs are only half-human half orcs. Orcs are not genetically compatible with anyone else and most half-human/half-orc children are still sterile most of the time.
In a lot of D&D settings, half-orcs are a basic race, listed in the Player's Handbook since 3rd edition. They sort of of are a basic race in Scarterra, at least among adventurers if not the general population.
In Scarterra, orcs are relatively common in West Colassia and they are rarely seen outside of West Colassia. That means most half-orcs are from West Colassia too. Even if they are not common there, most West Colassians have heard stories about Mordock the Destroyer, the half-orc that nearly conquered the whole continent, so your character will be recognized by any West Colassian for who and what they are.
Outside of West Colassia, humans and demi-humans aren't going to be sure what your character is. They may or may not be fascinated or frightened by your character's odd appearance and large size. Inside West Colassia, some are going to be fearful and distrustful of your half-orc just on sheer principle and others are likely to be accepting, it varies from individual to individual but also on the whims of the game master. If you want to roleplay dealing with discrimination issues, you should load up on related social Flaws, if that is not something you are interested in, don't. Also, tell your game master in Session Zero.
The vast majority of half-orcs were conceived by non-consensual sexual encounters but you don't have to dive into this aspect of your character backstory if you or the other player's are uncomfortable with it.

by Neshik's Player with Hero Forge

Half-orcs are naturally great warrior characters with their powerful Strength bonus. They suffer no penalties as a mage or divine magic caster. They get some penalties that are inconvenient for Rogue/Experts but these penalties are not insurmountable and it might be fun to play a Rogue that is also very good at hitting things. Half-orcs are a natural narrative fit for a lot of criminal groups for sure.

So you want to play a Man-dwarf ?

Mondarian man-dwarves are subject to some pity because they are sterile and Mondarians put a lot of weight into family and lineage, but they are generally treated with love and respect, or at least respect.
Outside of the Islands of Mondert, you are not likely to see multiple man-dwarves elsewhere. Most non-Mondarian dwarves recognize them at once. They also view these hybrids as sources of pity and have a taboo on humans and dwarves mating.

Most humans would have trouble recognizing man-dwarves for what they are thinking they are very large, somewhat odd looking humans. Most humans don't know enough about man-dwarves to be prejudiced against them, but some man-dwarves are mistaken for ogres and this often leads to tragedy.
If you are playing a man-dwarf PC you probably want to focus on how your character grew up and how your character met his/her social needs (or failed to meet them). It's not difficult to justify how such an outsider becomes an adventurer.

Man-dwarves are big, strong, and tough. That means they are natural fits for natural the warrior archetype. That said, there is no reason you can play a Rogue/Expert?], mage character, or divine magic caster who happens to also be physically large.
A lot of man-dwarves find their sense of belonging via a religious organization, so holy warrior archetypes are common among adventuring man-dwarves.

So you want to play a half-gnome?

Scarterran half-gnomes are either Elf-gnome hybrids or Gnome-human hybrids.

by Me using Hero Forge

In present times, the vast majority half-gnomes are the result of unconventional couples or casual flings. In the Red Era, most half-gnomes were the result of non-consensual encounters back when many gnomes were enslaved or otherwise made second class citizens. Most full gnomes have not forgotten their history and for all their talk of love and tolerance, they often treat half-gnomes with pity and derision. Most non-gnomes are barely aware that half-gnomes exist at all so they aren't really prejudiced against them.

Gnome-human hybrids have no special abilities and many have debilitating physical flaws, but a few win the proverbial genetic lottery and don't have any weaknesses able to essentially exist as a "human" with some somewhat distinctive facial features. If you want to play a chronically disadvantaged character, go for it, at least you get a few freebie points out of it. Most players aren't interested in a character like this, at least for a long-term campaign.

by Me with Hero Forge

by Me using Hero Forge

Elf-gnome hybrids are a little bit better off. They may lack the physical grace of elves and the social graces of gnomes, but they still face some social derision but they do have a special ability unique to them, they are very perceptive in every sense of the word. Many their career out of this, such as the politically astute Dreiters.

Dreiters the gnelf by Me using Hero Forge

Gnelves are very good at hearing the approaching ambushers, smelling the poison in the wine glass, spotting the loose scale the monster's hide, and reading the micro-expressions of the duke's seneschal to figure out what he's really thinking.
Most NPC gnelves end up in some kind of rogue/expert based advisory role, but there is no reason a warrior, mage, or divine caster cannot also be freakishly perceptive.

Gnelves have one fewer health level than most other characters and this can be inconvenient, especially for warriors, but it is not an insurmountable problem.

So you want to play half-human half-elf?

Humans tend to call them "half-elves" and elves tend to call them "half-humans." Human society predominates, so I will call them "half-elves." I am listing them in order of most common to least common.

20 d10s from Wikimedia Commons

Stat wise, half-elf characters function like human characters with an Alertness bonus. Or alternatively, they play like an elf character that swaps the Dexterity bonus out in order to nullify the health and saving throw penalty.
Any character archetype you can make for a human or elf can easily be adapted to a half-elf. The main difference is background

Half-elves are fairly common in Scarterra. There are the only half-breed in Scarterra that is numerous enough that they can create multiple societies of their own kind. That doesn't mean your character found his or her way into one. You can still play an awkward loner in search of where he belongs.
While I go over the five elven origins for half-elf half human, remember that Scarterra has over two dozen separate human ethnicities and this will influence your character as well.
It is often fairly easy for a half-elf to fake heritage he or she doesn't have and it is fairly easy for a half-elf to be misidentified by accident. If your half-elf character is in the interior of West Colassia, most people will just assume your character is half-wood elf. If your half-elf character is in East Colassia, most people will assume your character is half-dark elf, and so on and so forth. Some half-elves find mutable identities to be handy and others find it annoying. Many choose to wear the national colors their homeland while traveling abroad to avoid misconceptions.
So you want to play a half dark elf?
This is the most common variant of half-elves in Scarterra, and the vast majority of these half-elves, or half-humans, live in bondage.

by Me with Hero Forge

by Me and Hero Forge

Your character might be the result of highly unconventional couple or one of the few half-elves that are legally freed, but statistically speaking, most half-dark elf PCs are former slaves which is just gravy because ex-slave is a very popular character trope in fantasy settings, and that is probably the direction your are going to run with though you could play a half-dark elf that was raised by humans in the Colassian Confederacy and never was a slave though your character's human mother definitely went through more than enough trauma and hardship for one lifetime.
Whatever their origin, a lot of half-dark elves want to put distance between themselves and Kahdisteria and East Colassia in general so you can potentially find these half-elves anywhere.
So you want to play a Apseldian Half-elf

Apseldian half-elves are fairly unique for half-breeds. If your character is Apseldian, that means your character probably does not have a human parent and and elf-parent. That means your character probably has two half-elf parents and grew up in an area where half-elves are the majority population.
Ironically, Apesldian half-elves can easily become arrogant racists that look down on the other races. Something that is uncommon among half-elves in general. Most Apseldian half-elves are not arrogant racists but most half-elves that happen to be arrogant racists are Apseldian. That said, having national pride does not automatically make one racist or jingoist or any of the other "ists".
Apseldia itself is centered around a very busy trading port so most Apseldians are exposed to a wide variety of people and cultures on a routine basis.

by Me with Hero Forge

by Me with Hero Forge

Apseldians believe in things other than the racial superiority of half-elves, they also believe in personal freedom and meritocracy. The government of Apseldia is easily the largest, most stable, and most powerful republic in all of Scarterra. It's also one of the few places where the Lanterns of Zarthus are "the Man" as opposed to the guys railing against the the Man. True to form for Lanterns and Lantern-sympathizers, many Apseldians want to export their republican model of government abroad, even if half-elves aren't involved.
It is pretty easy for a half-elf born outside of Apseldia to a human-elf pairing to apply for Apseldian citizenship and be accepted. Even so, such a character will still have had a childhood in one of the other half-elf cultures and they will be a big factor shaping her personality and outlook.
Apseldia is a trading port with ships coming in from every corner of Scarterra and ships leading to every corner of Scarterra. It's pretty easy to write a backstory to explain how and why your Apseldian PC made it anywhere your RPG campaign is set in.
So you want to play a half grey elf
The Elven Empire is run by grey elves but grey elves only make up about 30% of the total population overall and humans make up about 50% of the total population. Despite some taboos about human-elf coupling, half-elves are fairly common there.

Attitudes towards half-elves vary widely among the full humans and full elves of the Elven Empire, varying from person to person and region to region. These views run the gamut from despised pariahs to highly valued and even treasured individuals and everything in between. Due to some recent reforms, both written unwritten, a few lucky half-elves with highborn elven parents and managed to claw out positions of wealth and status but this is not the norm

by Me with Hero Forge

Half Elf Sailor by Me with Hero Forge

The Elven Empire is based on maritime trade. It's not uncommon for any imperial citizen to have experience on a sailing ship, but a disproportionate number of half-grey elves become sailors. Since sailors travel around, this is a good springboard for how and why your half-grey elf PC became an adventurer. It's not hard to come up with a plausible backstory for how and why your character ended up far away from the territory of the Elven Empire.

So you want to play a Half wood elf?

A half-wood elf raised by humans may or may not be able to fit in with the humans around them, and they may or may not develop loner or nomad tendencies. Most half-wood elves are the result of a sexual encounter on a wood elf's Rumspringa. When this happens, the elf parent might stick around until the half-elf child reaches the age of majority or close it it, or the elf might take the child home to Codenya (or give birth there), or the elf might leave the baby entirely. It depends entirely on the individuals involved.

by Me with Hero Forge

A half-wood elf raised by humans may or may not be able to fit in with the humans around them, and they may or may not develop loner or nomad tendencies.
If a half-wood elf was raised in land of Codenya, they will probably have their own Rumspringa and that can be a good springboard to becoming a PC adventurer, or the half-elf may decide to leave and never come back.

Wood elves are often wanders by nature, if any half-elf can manage to keep a foot in both the human world and the elven world, it's a half-wood elf. They can periodically travel between both cultures. It's not easy, but it is possible, and it certainly is a good basis for a PC concept.

by Me using Hero Forge

So you want to play a half-satyr?
Satyrs are famous for their libidos and a great many satyrs prefer sleeping with non-satyrs over sleeping with their own kind. When two satyrs have intercourse there is a high chance of conception occurring but when satyrs sleep outside their race, the chance of conception is much smaller. That said, satyrs sleep around enough that Half-Satyr Babies are still relatively common.
The first satyrs were descended from elves. When satyrs and elves conceive a child the result is usually an otherwise ordinary satyr that is somewhat more cerebral than the average satyr or an otherwise ordinary elf that is somewhat more physically robust and extraverted than the average elf.

When a satyr and a human conceive a children, the result is usually an otherwise normal half-elf that happens to have fast growing hair, is a bit taller and more athletic than average, and likely has a strong pull towards life's carnal pleasures. Half-satyrs are often prone to taking on risks and physical challenges making them a natural fit for many PC adventuring parties.
About one-in-five so-called called half-satyrs have tiny horns. No half-satyrs have goat legs, but a few unlucky individuals have a club foot.

by Me with Hero Forge

by Me with Hero Forge

A few half satyrs, especially those with horns, find their "tribe" with full satyrs but most choose to assimilate into human or half-elf society. Most half-satyrs are fairly charismatic and personable and can fit in to many places but they may or may not have trouble building very close relationships with individuals, often preferring to gravitate towards groups.

I want to play a WEIRD half-breed!

by Eron12 with Hero Forge

The game master can veto any player character concept, that doesn't fit in a chronicle, even an ordinary human. You need game master permission to play a half-dragon, half-spirit, or half-fae character. If I'm the game master, I'm okay with this as long as you want to use this to enrich and develop your character, and not because you want gimmicky powers or even gimmicky flaws.
Scarterran half-dragons exist. They are not common, but the children and grand-children of half-dragons retain some draconic traits. To some extent the same applies to half-spirits and half-Fair Folk. One minor difference is due to magical and spiritual influences and/or warlock pacts, it is possible for a character to have inherited fae or spirit trait even if her ancestors never had sex with a spirit or Fair Folk. Although spirits and Fair Folk occasionally do have sex with mortals, it doesn't always conceive half-breed children when they do, so half-spirits and half-fae remain rare.
Note unlike most half-breed types, half-dragons, half-spirits, and half-Fae are usually not mules. You can easily play a character who is a 25% or less of exotic heritage rather than a literal half-breed and still have exotic traits.

20 d10s from Wikimedia Commons

Characters with draconic, spirit, or fae legacy ancestry are often very different in many ways but in terms of character creation, they are all fairly similar in that they are dissimilar. You can mix and match exotic and normal traits.
Not every half-dragon has enhanced strength. Not every half dragon is large, not every half dragon has a breath weapon, and not every half-dragon has wings and/or a tail. Same thing applies to mortals with fae or spirit ancestry. In-universe, it's a crap shoot what traits the character is born with but out of universe, the player decides what traits the character has (with game master approval of course).
You take an ordinary human, or an ordinary gnome, or ordinary tengku or ordinary whatever with the same character creation rules of a "normal" character and then load your character up with a bunch of exotic Merits and Flaws, carefully picking traits that enhance your character concept.
It is difficult to show restrain in this case and it's not unusual for a player to end up spending over half their freebie points on these exotic traits. This means the character is likely to start out with fewer mundane abilities than his more conventional party members.
Scarterra doesn't have Tieflings or Asamar and the like, but half-spirits are essentially the same basic concept. A mortal character with spirit heritage is going to have physical and/or psychological traits stemming from one of the Nine, sometimes in a cliched way, sometimes in a subtle way.
The type of spirit matters too. Mera doesn't have as many warrior spirits as Hallisan does, but the half-spirit offspring of a Mera warrior spirit might have more in common with the offspring of a warrior spirit of one of the other deities than she has in common with the half-mortal offspring of a Mera healing spirit.

You need to figure out how your character has similar traits to her spirit parent and how she differs. Also, most half spirits are staunch worshipers of their associated god or goddess but not always. Some rebel completely. You need to figure out where your character fits into this narrative. You can figure out who your character's spirit ancestor first and derive character traits from that or you can pick character traits and reverse engineer a spirit that would logically pass on those traits to his/her offspring.

by Neshik's Player with Hero Forge

I want to be play a character who is 25% human, 25% elf, 25% fae, 25% dragon, and 25% spirit!

Is it physically possible for a half-dragon to make a viable healthy baby baby with a half-spirit or half-Fair Folk?
Yes.
Are there are at least three or four characters with this much weird lineage running around Scarterra somewhere?
Yes.
Can one of these three or four people be my player character?
No.
At least not in any game I'm running. I'm not a big Meany-Head, I just don't want the most interesting thing about a player character to be the fact that the character exists at all. A player character should be defined by his/her actions and personality first and foremost and his/her identity and background second.

The metaphysics of Scarterran half-breeds are in The birds and the bees of Half-breed mortals