Warning: This isn't 100% finished but you can at least get the gist of everything.

Set 1
Owls are seen as bad omens in Chinese cultures, and as such, Lin is often persecuted as a child. However, she is also a fairly powerful individual, and a martial arts prodigy. Her stubbornness and headstrong nature, allows her to push past the ridicule and eventually become fairly well known in Shengxiao.
While travelling through a city one day (I’ll name this later), she hears chatter of a powerful rabbit soothsayer that has suddenly surfaced after 100 years of meditating. Eager to learn about her amazing future life, she decides to see the soothsayer so she can boast to her friends. To her surprise though, her future is not bright. In fact the rabbit tells her that she did not escape her fate, and as a bad omen she eventually causes a great calamity upon the world. He tells her that demons have showed up in each nation, wreaking havoc each night. He also tells her the only way to stop this calamity from befalling Shengxiao, is to journey into heaven and borrow a mystical sword made of the purest jade, that acts as a key to seal the demons back in hell.
Unfortunately, this was a plan concocted by the rabbit nation. Normally a group of docile scholars, over the years they have been increasingly ignored by the other tribes, and have finally decided to exact revenge on the world. Learning that the king of hell, a bat demon who has taken control of hell from the goats, is sick of everything being so bright, they come up with a plan. Trick some foolish hero to steal the jade key from heaven, and use it to unlock the chains holding the moon in the sky, throwing the balance of heaven and earth into chaos, plunging the world into eternal darkness. Even more unfortunately for the rabbits and demons, darkness itself is actually an even more powerful entity that was banished by the gods when they created Shengxiao.
Distraught, Lin seeks out the wisest of the birds, and after telling them what happened they tell her that she must travel to each nation/tribe/whatever, learning each’s special skill to be able to complete the nine trials at the gates of heaven. So she does, and masters the 9 forms. Upon reaching the gates of heaven though she discovers there is in fact 10 trials. Defeated but not discouraged, Lin begins her quest to find the 10th tribe. Eventually coming across a long forgotten lake connected to a great cave system, where the aeons old turtles are waiting for her. They teach her whatever the final lesson is.

Set 2
Arriving in heaven at last, our hero is immediately taken by guards. But of course she wouldn’t go down without a fight. She incapacitates over 100 soldiers of heaven when she is subdued by one of the gods (needs a name) overwhelming power. The god congratulates her on getting into heaven and defeating so many guards, and tells her it’s all a misunderstanding and they were just taking her to a great banquet in her honor. Because of course, heaven only a few visitors every 500 years. During the feast she tells her story, about the trouble and her journey. The gods basically dismiss her, telling Lin she doesn’t really know what she’s talking about.
-Everything after this point is pretty rough-
Eventually she finds the item and has a big battle with the gods but just barely makes it back to earth and hands the item to the rabbits.
Rabbits unlock moon chains and the darkness consumes stuff or something (Maybe make this less eldrazi sounding?) The moon falls into the sea and balance is broken.

Set 3
Hero gathers up any friends she can that don’t blame her for everything and the gods let them into hell through the secret back entrance since it’s her fault anyway, so she better solve everything and whatever.
Stuff in hell.
Beat up the bat guy “You want sleep?” *punch in the face* “Sweet Dreams.”
Heroes emerge from hell. Rabbits are taking over and gaining power, gods are busy holding back the darkness. Heroes fight the rabbits and demons and stuff, at the last moment the rabbits get the ancient weapons or whatever they need to incapacitate the gods.
Hero finds her true power or something. Maybe she is a walker or becomes a god, or whatever.

In Heaven

Dragons - Royalty in the kingdom of heaven. All dragons are originally born from the creator god. Because of this they sometimes forget about the needs of other creatures. They gave knowledge of metalworking and fire to the mortals, as well as the power to extinguish it. ( obligatory rain reference)

Phoenixes - Based on http://en.wikipedia.org/wiki/Fenghuang. They are the personification of balance, life and death, etc. Souls pass through their fire before they can reach heaven or hell, purifying them. They are the lawmakers of heaven, and decide how the heavenly bodies move through the sky. They literally became the fires of the forge that crafted the chains to hold the moon in the sky millennia ago.

Kirin - They are the court of the kingdom of heaven. They judge the dead to decide where they go. More equine than draconian in this story. Think a little closer to the kamigawan kirin than traditional chinese ones.

Frogs - Based on http://en.wikipedia.org/wiki/Jin_Chan Great frog spirits made of gold. They bestow wealth and long life on those who are pure of heart or otherwise worthy of blessing. They carry rosaries made of silver coins. In charge of the finance of heaven and hell. They provided the purest precious metals to forge the chains.

(Elephants as the guardians and soldiers of heaven maybe)

All gods are mostly white, may have splashes of other colors but that is unlikely.

On the earth

Rabbits - Docile little scholars and scrollkeepers. They live in burrows like hobbit holes, but generally on a much grander scale. Secretly plotting with bats to overthrow the balance because they are sick of hiding underground. Their burrow homes put them in close proximity with hell, which probably influenced them over the years. Mostly UB

Monkeys - Live in the mountains and forests of shengxiao, and can sometimes be seen leaping across buildings in the cities. Most other races consider them annoying but not a threat. Their kung-fu is not to be underestimated though. Gorillas and other apes are usually hostile, but because of this they don’t get to mate often and very few of them exist anymore. Mostly GR

Birds - With the bird’s ability to learn quickly and mimic actions and voices of other creatures/peoples, they can be seen pretty much everywhere, most live in a giant city that acts as basically a college, like a modern monk monastery. Very religious? Mostly WU

Cats - Very advanced culturally, with a strong court system that involves duels. They choose to live very tribally to stay close to nature and keep their minds and bodies sharp. Mainly tigers, but some lions and other more exotic cats do pop up rarely. Their leader has a slightly canine appearance, to mimic the lion dog statues of ancient China. A very territorial tribe. Mostly GW

Snakes - Very secretive and shamany. Lots of assassins for hire and stuff, but their assassinations are bathed in tradition. Think the brotherhood from skyrim. Needs more description! Mostly UB

Rats - You can’t go into a shadowy alley, dying forest or wheat field without finding a rat. And when you do, it will probably try to sell you something. Among the rats there are also mice who tend to be very skittish. A mouse will only be found if it wants to be. Some say they can even pass in and out of this world when scared enough, but that’s probably just myth. They start as black, move to red when cornered i.e. the third set.

Pandas - As phoenixes are the heavenly embodiment of balance, pandas are the earthly. they have strong ties to reincarnation and feng shui. Most pandas follow an ancient religion that has been practiced since the beginning of time, where they essentially track their entire lives to determine what they will become in the next life. It is said their leader has been reborn as the same person 333 times over. Mostly BW

Turtles - Ancient teachers that live deep in a temple at the bottom of the deepest lake on the highest mountain. Most of their lives are spent meditating, only acting when necessary. Even in the heat of battle. Mostly UG

Horses - Sentient horsepeople like wishmonger from MM. The fastest and strongest legs in the land. Their horse stance is unmatched. They are generally a neutral party, serving as messengers and historians, sending information faster than anyone except the gods themselves. They once walked on four legs as slaves to other races. Eventually breaking free and blah blah. Now instead of shame and pain they have pride and use the four legged running method when a delivery needs to get there super fast. Mostly WR

Mantii - When a being dies mantii are tasked to carry that soul until heaven can process it through the reincarnation wheel. Stronger souls can escape and end up being banished to hell or offered a job in heaven. Much less insectoid than nantuko or other insects. They still have mantis claws and a somewhat mantis-like face, but their lower body is much more human. Think insect body morphed into a human shape. As they grow older their backs hunch more and more giving them a more mantis-like quality. This is from carrying souls most of their adult years. Mostly GB

UR is not represented on any tribe on purpose. Balance within the sets is achieved by using spells and splashing things into other colors.

In Hell

Goats - Not evil really, more of a Hades type deal. They simply got the job of keeping hell in check.

Demons - The only non-animal race. Their appearance is similar to the devils on innistrad crossed with the goblins of lorwyn. Very annoying and love to play tricks. Based on some of the less evil demons in chinese myth

Bats - The current king of hell and his “army” consist of bats. They want darkness to rule again because the fires in heaven hell and earth are keeping them up all the time. Yes, the driving force behind the destruction of the world is sleep deprivation.

Pigs - Natural denizens of hell. Just like normal townsfolk on the plane, but in hell. Generally gluttonous and perverted but not all of them. Less virtuous but not quite evil souls often become pigs in hell, where they must literally work off their debt until they earn enough money to buy their way back to life.

Hell Tribes are all black splashing various other colors.

Yaochi - Heaven
Di Yu - Hell

Tian - Name for the gods. Means cosmos

Wurm’s Hovel* - a huge collection of tunnels and burrows where rabbits reside and rats
hide in. This proximity to the darkest parts of the earth are what slowly drove the rabbits to evil doings. They are literally just too close to hell.

The crying forest* - Many souls are destined to take a certain path, while others are less fortunate and remain as ghosts until heaven gets around to doing stuff with you. This is where the mantii come in. All ghosts eventually wander into the crying forest as they have for millennia, and eventually the mantii took notice and pity on them. You know the rest of the story. The forest mostly consists of willow trees. No grass ever grows, and only a few flowers grow in special places.

Devil’s Playground* - A dangerous collection of forests and jungles where many less friendly monkeys and snakes make their homes. Legend says the demon king’s beard grew too long one day and punched a hole straight up into the world. When he finally cut it off each hair turned into a winding twisted tree.

Jungle of the closed fist - Tiger clan home

Guild leaders

Guild Heroes

*placeholder names

Mechanics
Set 1
Horses - Courier (When this card enters the battlefield, exile the top card of your library face up. When it leaves the battlefield put the exiled card on the top or bottom of it’s owner’s library.)
Tigers - Pounce (COST, Return a blocking creature you control to hand: Put this card onto the battlefield from your hand blocking each creature the returned creature was blocking.)

Mantii - shepherd (When this card enters the battlefield, you may exile a creature card from a graveyard until this card leaves the battlefield)
Snakes - Unmask (It’s ninjutsu)
Birds - Meditate - At the end of your turn, if you cast no spells this turn, [triggered effect].
Combo (When you cast this spell reveal the top card on your library. if it’s an instant or sorcery card, put it into your hand. It costs 1 less to cast this turn)
Fight
Set 2
Gods - Celestial (When this creature dies exile it. You may cast it from exile by exiling a card in your hand in addition to it’s normal costs.)

Rabbits - Scheme - You may choose not to untap ~ during your untap step. If you do, [effect]

Rats - Rummage - keyword action thing (To rummage, exile the top card of each player’s library)

Monkeys - Chi Mastery (When this creature attacks, exile cards from the top of your library until you exile an instant card that costs less than this creature’s attack. You may cast it without paying its mana cost. If you do, prevent all damage this creature would deal this turn. Put the exiled cards on the bottom in a random order.)

Pandas - Rebirth (When this creature dies, you may return target creature card with converted mana cost X or less from your graveyard to your hand.)

Turtles - Zen (When this creature is dealt damage, draw that many cards)

Burn spells that deal combat damage

Set 3

Repentance COST - Condition (Cost: Exile this card from your graveyard with 3 pain counters on it. Whenever you CONDITION, remove a time counter from it. When the last is removed, cast it without paying its mana cost. Repent only as a sorcery.)

“Dies in battle” Combos with combat damage + fight