Norihiro and Yagi
Three hundred years ago, the small nation of Norihiro found itself under attack by the Realm. Although the people of Norihiro were learned in sorcery, necromancy, and other stranger things, they could not stand against the Dragon-Blooded - or as they called them, the Asarakam. In desperation, the magicians of Norihiro appealed to Ma Yuan, one of the souls of Metagaos. And Ma Yuan taught them a secret: through certain rites that made use of the flesh of captured Terrestrials, the magicians could create a parasite that would turn a man into a monster called a Yoma.
Yoma were stronger and faster than human beings and had a degree of control over their own flesh. But they were mostly uncontrollable, ruled by their desire for human meat. So Ma Yuan taught the magicians a second secret: by mixing the flesh of a Yoma with that of a human, they could create enhanced warriors. Those warriors had strength and speed to challenge the Exalted, and their regenerative abilities exceeded those of even the mightiest Dynasts.
Unsurprisingly, Ma Yuan's gift had a catch. The half-Yoma warriors eventually succumbed to the monsters inside them, changing shape and becoming terrible creatures that feasted upon human guts. These "Awakened Ones" were far more dangerous than mere Yoma and could not be controlled at all. They drove back the Realm, temporarily, at a terrible cost to the people of Norihiro.
The magicians knew that could not win the war unless they could control their monstrous creations. And so they traveled to an isolated island called Yagi in the far West. They turned the Yoma loose upon the population, then stepped in with an army of half-Yoma who would protect the common people - for a price. They would use Yagi to test their warriors, secure in the knowledge that warriors who Awakened would never find Norihiro. In fact, they would never know that Norihiro existed, or why they had been created; the magicians drew new warriors from orphaned children of Yagi, and taught them that their duty was to protect humanity from the Yoma.
The war between the Realm and Norihiro ran hot and cold for almost two centuries. As the Realm gradually took the conflict more seriously and devoted more resources to it, the magicians developed their living weapons ever further. They began to use women exclusively as warriors, having found that they were slower to awaken. They trained twins to fight together, with one awakening temporarily while the other held her soul and preserved her sanity. And by mixing the flesh of Awakened Beings with that of mortal women, they created mindless killers called Abyss Feeders.
All the while, Yagi bled. The population of Awakened Ones steadily increased and the population of humans steadily declined. Until the warriors of Yagi learned the truth. Upon discovering that their masters had created the Yoma, they rose up and slew the magicians.
Making matters worse for Norihiro, the Realm was not blind to their experiments. The Dragon-Blooded spy Tepet Rubel lived among them on Yagi, reporting on their research to the Realm. He stole the secrets of Yoma creation, and smuggled the corpses of Awakened Beings from Yagi to the Blessed Isle.
In the end, Norihiro was destroyed. The Realm created and unleashed its own Abyss Feeders, knowing that the common people of Norihiro would assume that the magicians had finally lost control of their monsters for good. The nation dissolved, partly due to monsters eating it and partly due to a grand rebellion.
In the aftermath of the war, the Empress ordered all records of the Realm's use of Yoma destroyed. And her orders were for the most part followed. But the war's end was less than a century ago, and there are still living Terrestrials who could make Yoma if they felt the need to. Most of them live in Norihiro, ruling a now peaceful, but thinly populated and monster-infested, satrapy.
Yagi, meanwhile, is experiencing a renaissance. The warriors Norihiro created took their fraudulent mission and made it real; they've wiped out the Yoma of Yagi and are well on their way to wiping out its Awakened Beings. Under their protection the mortal population has grown in numbers, wealth, and culture. Their own numbers have dwindled, however, and many of them worry about what will happen if the last of them Awaken. Some have seriously considered the idea of a mass suicide.
Mechanically, Yoma aren't too interesting. They're basically just people with good combat stats and the occasional minor shapeshifting ability.
Half-Yoma should be designed as a fully playable splat; I'd give them a half-suite of Attribute Charms, limiting them to Strength, Dexterity, Stamina, and Perception. Strength and Dexterity for combat Charms and Athletics stuff, Stamina for regeneration and extra health levels, and Perception for sensing Essence. They wouldn't have very many standard Charms, and each would be quite expensive xp-wise. You'd generally expect an Essence 3 Half-Yoma to have all the standard Essence 1-2 Charms. Limit would make them stronger, and could be taken voluntarily, but Limit Break would cause Awakening. Power level would scale strongly with Essence; an E1 Half-Yoma would be weaker than an E1 DB, but an E5 one would be stronger than an E5 DB (in combat, since half-Yoma don't do much else). Half-Yoma would also have the opportunity to make unique personal Charms, giving them each a signature move or two.
Awakened Ones would just be half-Yoma with some "I'm monster-shaped" Merits and 10 permanent Limit. Maybe also a bunch of extra Health Levels.
