Ling’s background begins with the sort of world he lives in, Its differences placing it clearly very separately from our known Earth. For one, more prominently, Ling’s world practices sciences known as Rentanjutsu, or Alchemy as it’s known in the neighboring country of Amestris. Both arts would seem to appear near to magic when preformed because with them, you’re able to take matter, and while not adding or taking away, you’re able to change it into something else. Alchemy, used in Amestris, is geared more for war use and fighting. Rentanjutsu, the art of Ling’s home country, Xing, is used more towards healing purposes.
Ling’s home country is fairly peaceful when it comes with dealing with other countries, unlike Amestris, which is currently warring. However, on the inside, Xing is extremely conflicted. It consists of over 50 ethnic clans, and each clan’s duty is to produce an heir by sending the eldest daughter of each clan to the emperor to become his concubine. Once each clan has a respective heir, the battle for the favor of the emperor in hopes of becoming the next ruler of Xing and bringing prosperity to their clan begins.
Born as the twelfth son out of the fifty to the current Emperor of Xing, Ling Yao learned early on that life was quite dangerous as an heir. As the representative of his clan (the Yao clan), Ling's had to evade hundreds of assassination attempts and other dangers growing up thanks to the hands of his several other siblings. This not only led to Ling learning important survival skills but also insured he was given trustworthy and dedicated bodyguards.
Roughly around the time Ling turned fifteen, the Emperor became deathly ill. He wasn't given too much time to live and thus the fight for the throne became far more urgent. In fervor to gain the favor of the Emperor, Ling set out for the secret of immortality. If he could give his father a glimpse of it, then it would be enough to up his status so that he could take the throne himself.
So, thus, Ling began his journey to the west!
With his two trusted bodyguards, horse, and camel, Ling set off through the desert. Hearing several rumors about the Philosopher’s Stone and its possibility of granting never ending life, the prince decided to head for Amestris.
Braving through the harsh conditions and stopping at the Cselkcess Ruins for a quick pit stop, the group finally made it to the country in the west.
Ling’s first real encounter with the country’s people, ironically enough, were Edward and Alphonse Elric (Two Alchemists with an extensive history with the Philosopher’s Stone.), Al having found him collapsed in an alley from hunger. After taking him to a restaurant, Ling then somehow managed to con a meal out of them as well as some information about the stone. Not much, but enough to make it sound more ominous than he’d originally thought, seeing how it took Ran Fan and Fuu putting a knife to their necks for them to say anything.
Of course the ordeal ended in a huge fight in which most of Rush Valley became wrecked beyond recognition.
After the Xing travelers made their hasty escape, leaving the Elric brothers to worry about all the damages, Ling once again ‘passed out from hunger’ and was found by Garfiel, Winry’s boss and teacher, thus allowing him to run into the Elric brothers again. (Though Ed was none to pleased and banged him in the face with his broken automail.) And somehow or another, they all agreed to ride to Central together, each with their own agendas.
Ling’s agenda still being the Philosopher’s stone, he took off on his own to look for it. Sadly, this only got him arrested for not having a passport into the country when a police officer found him ‘passed out’ in the street. Without another word, Ling was dragged off to prison.
Once there, Barry the Chopper broke Ling out, promising him something worth his time for helping. That done, he escaped with said serial killer and 2nd Lt. Maria Ross, who’d been wrongfully convicted of the murder of Maes Hughes. With some careful plotting, they were able to fake her execution by Roy Mustang, and secure Ross a safe way out of the country. With that out of the way, Ling made his way back to the apartment Barry was being kept in with Falman and proceeded to contact his vassals via smoke signals, much to the distress of Falman. (Their location being a secret and all.)
With the three Xing travelers reunited, Ling introduced them. After not getting any information out of Barry on how he got his body (It was nothing but a suit, Ling left the apartment, giving Ran Fan and Fuu the instructions to signal him if anything interesting happened.
Ling’s next destination was the Elric’s hotel room, popping in through the window just as Armstrong was dragging Ed off for official business (and damn near giving Winry and Al a heart attack). He told them what Armstrong had in mind for Ed. Moments later a flare went off in the sky, letting him know something was starting to go down in town. He asked Al if he was coming, for there might be something interesting for him, too. Al agreed, and the two were off.
Following the signal, Ling and Al found Ran Fan fighting off the shape shifter Envy, who was bewildered that his shape changing was doing virtually nothing against his eastern foe. This being because both Ran Fan and Ling could sense the great amount of souls stored within Envy and his Philosopher’s Stone. The rest of the fight did not go in Envy’s favor until Ran Fan and Ling started to wear down, finding it rather hard to kill the homunculus. It only ended when Pride decided to step in from the shadows. While not showing his face just yet, he commanded Envy (and Gluttony, who had joined the fight prior) to step down and leave. Ling was just a little relieved.
Al, Winry, Ling and Ran Fan regrouped at the hotel room soon after for a small discussion, which lead to the others finding out about Ling’s princely status. He let the unusual laughter slide (Why were they laughing? People are usually more awed!) in favor of flirting with Winry, who playfully banged him with a wrench. (sigh)
The conversation, however, went suddenly downward as Ling pressed the matter of immortality and its connection with Al’s current body, insisting on learning the secrets of it (he learned quite a bit about the brothers through Barry the Chopper). Al refused to tell him anything other than it wasn’t worth it. When Ling wouldn’t back down, Winry stepped in and the conversation ended.
Later, Ed returned from his ‘business in Resembool’ and caught Al up on all he found out. Ling somewhat peeked in on the conversation (Meaning he hung from the hotel room window and listened to the whole thing.) and when they talked of luring out the homunculus by confronting Scar (whom was still alive), he jumped in (literally) with a plan to help both parties. Ling wanted a homunculus (and thus, immortality), Ed wanted to get at Scar after hearing he was the murderer of Winry’s parents.
The parties made the deal and set off.
Ed first started to lure out Scar by openly using his alchemy. This got Scar out of hiding easily enough, and with the commotion, the homunculi made an appearance in the back to observe. Thanks to Ran Fan and Ling’s ability to sense the large amount of souls within them, they were easily spotted.
Before anything could be done, though, the Fuhrer interfered. Since Bradley’s structure was different from other homunculi, neither Ran Fan or Ling could tell what he was until it was far too late. Lightning quick, Bradley shot up to where Ran Fan was standing and took out her arm before she had a chance to defend herself.
Now if there was one thing you did not do, it was injuring one of Ling’s bodyguards. After decapitating Gluttony, who was on his way to finish her off, Ling threw Ran Fan over his shoulder and tried for a hasty get away. Bradley, finding his dedication to her amusing, tried to take him out while carrying her weight. Ling fought back rather well, considering. At least until Gluttony reformed and knocked him and Ran Fan through a building.
Once away from the public eye, Bradley then tried to interrogate Ling on what it was he was after. Ling gave him nothing and continued to try and escape with Ran Fan. Bradley told him to drop his dead weight, informing him that the only way to make it to the top was to leave the weaker behind. Ling was appalled by the thought of that, calling Bradley a fake king for his philosophy. Moments later, Ran Fan set off a flash bomb to cover their escape. Unfortunately, Bradley’s other eye wasn’t being covered by an eye patch because it was injured. It was hiding his Ouroboros tattoo.
Managing to barely escape the building by setting off a grenade, Ling put as much distance between him and Bradley as possible. Turning down several streets and alleys while being heavily pursued by Gluttony, Ling realized that he’d run into a dead ended street devoid of any witnesses. It was a well-laid trap by the president.
Ling was at a loss for what to do (as they were catching up quickly), but Ran Fan, who realized they were tracking their blood scent, took matters into her own hands. She severed her injured, useless arm much to Ling’s astonishment and protest, and tied it to the back of a stray dog. With the homunculi running a dry trail, Ling escaped from the president.
Gluttony, after probably getting bored with the trail, caught the scent of Scar and went after him for a meal instead. Jumping down into the middle of the Ishbalin’s fight with Ed, Gluttony made a startling appearance only to have his plans cut off by Ling emerging from the manhole on the street, landing atop of him, and cramming a lit grenade into his mouth. The Homunculus exploded all over the street.
Seconds later, Ling demanded a steel cable from Ed. Ed quickly made one up, and Ling tied the reforming Gluttony into a neat ball of fat before he could finish, successfully restraining him from any movement whatsoever.
Ling had caught the brothers a homunculus just as he had promised.
Later after everything had blown over and Ran Fan had been retrieved from the sewers, everyone met up in a secluded place so that she could be properly treated and what to do next could be discussed. Before much could be said, however, Gluttony broke free of the restraints after noticing Mustang was present (Mustang had killed Lust earlier on, and Gluttony had been rather distraught over all of it). He changed into his true form, which consisted of a mouth that took up his entire body and an eye in its center, and began to suck up everything in the area as if he were a vacuum.
Ling, Ed and Al quickly saw everyone off so they could deal with the mess without endangering the injured (who had escaped via car). Though, once done, the three really had no idea how to battle out the enraged Gluttony.
That was until Envy showed up and calmed the crazed homunculus down enough so that he could follow orders. His next order, of course, was to eat Ling.
Ed transmuted a wall separating Gluttony from Ling, leaving him to deal with Envy while the Elric’s decided to try and restrain Gluttony.
Ling’s fight with Envy proved to not be as easy as he would have hoped, having to resort to tricks like kicking dirt into his eyes to keep from getting strangled to death by Envy’s shape-shifting snake arm. In the middle of a stand off, Ed and Al were thrown by Gluttony into the general area of Ling’s fight. As the prince turned to glance at them, Envy rushed him in an attempt to cut him off guard. Ling saw him coming and then promptly hacked off his leg. Successfully putting the homunculus on the ground, Ling moved in for a finishing blow.
But then, Envy shifted into Ran Fan and Ling hesitated. Envy used this to call Gluttony, who was still in vacuum mode, to dispose of the irritating human prince. Ed jumped in the way to pull him to safety, and Envy seeing Ed about to get sucked up as well, made to grab his leg, for he had strict orders to not eat the Elrics.
Ling woke up in what he could have guessed was Gluttony’s ‘Stomach’. It was an endless abysse with no walls, only a floor, which decoratively enough was a sea of blood. It wasn’t until after he and Ed met up with Envy that they were informed Gluttony’s stomach is a mock Gate Father failed to create. They were basically stuck in another dimension. Huh.
Of course Envy also mentioned they couldn’t get out and they were all going to die. A fight broke out and the Sin showed them his true form. It was terrifying to say the least and as strong as it was ugly. Ling and Ed got their asses kicked six ways to Sunday until Envy managed to actually eat Ed, in which there, the little prodigy figured out how to get them home. None too soon, too, since Ling already suffered a few broken ribs from the fight and a good bit of internal bleeding.
Using a bunch of alchemy mumbo-jumbo that Ling really didn’t understand, Ed opened the REAL Gate and they all hopped through, hoping to get them back home.
And it did! Sort of. It spat them out in the middle of the Homunculi’s evil lair.
Confronted by the creator of the homunculi, someone simply known as Father, another fight broke out. This time because Ling was, once again, in their way. And they fought back pretty hard! But, Father not only physically nearly beat Ling to death with giant pieces of the floor coming up, but he made it so Alchemy couldn’t be used within the City.
To put it very simply, Ling was fucked. With Gluttony pinning him down on his already shattered ribcage, Father stepped over and offered him a choice. Die, or put his body to use and become a homunculus.
Well, considering all things, Ling wasn’t about to turn him down. Hello? The Philosopher’s Stone? Immortality? The entire reason for coming to this damned country to begin with? Oh and the fact that he was bleeding to death.
Ling gladly took his offer and Father forced a liquid Stone into the cut on Ling’s face.
Unlike previous Stone or would be Stone vassals, Ling accepted Greed into his body and the two began a sort of strange mutual co-existence. Ling chilled out in the back of Greed's head waiting for whatever opportunity he could to take back his body. Greed meanwhile hung out in Father's lair, having all his memories erased from his earlier existence, standing guard like a good homunculus son.
Until Greed killed the last surviving member of the Devil's Nest and all his memories from before came rushing back. Half crazy, Greed attacked Bradley, the one who slaughtered all of his men, and the two had a vicious fight until Ling snatched control of the body and got them out of there before they were both toast.
Ling dragged his ass out to the only place he could think of to go at the time, the old shack where they had met up after that mess with capturing Gluttony. There he ran into Ed and two chimeras. After eating all their food he proceeded to tell them some of Father's plans before Greed yanked back control.
After a brief conversation, Ed and the Chimeras agreed to join up with Greed and the four of them set of to do shady and sneaky things.