I do not own the copyright to Fullmetal Alchemist.

This is an alternate-universe story that begins during the battle with Lust in Laboratory 3 (Chapter 39 of manga, Episode 19 of the Brotherhood anime) and will parallel the series to the end. Spoilers for the whole thing. Rated T for violence, mild profanity, sexual innuendo, and implied threats of rape (nothing graphic or really bad).

Extra disclaimer, since I received a complaint: This story takes Mustang to some dark places. When possessed by Wrath, he does cruel things, including to Hawkeye, that some may find upsetting. This is a dark drama/adventure story with a Royai relationship at its heart, not a fluffy Royai romance. You have been duly warned.

And I know, this is about the millionth "Character X becomes the new homunculus Y!" story ever written. But I hope you like mine anyway. :)

Chapter 1: Contingency Plans

Father was angry. He wasn't accustomed to feeling such a primitive emotion, and that made him even angrier. The entire situation was unacceptable.

There had been a freak accident, an explosion in an ammunition facility just as Wrath was touring it for inspection. The chain reaction had been so large that more than eighty humans had been killed. Wrath, with his superior vision and speed, had nearly made it out of the blast radius in time—nearly. But he could not avoid being overwhelmed by falling debris as an entire building collapsed on top of him, and he was found crushed under a concrete beam, barely clinging to the last shreds of life. He was bonded to a fully human body, and unlike the other homunculi, did not have the ability to regenerate.

At least his essence had not been lost. There had been just enough time for Father to reabsorb the Philosopher's Stone that coursed through the bloodstream of Wrath's human host. Once that was done, he had left the crushed shell of the man known as Führer President Bradley to wither and die, not giving it a second thought.

There were no suitable hosts left alive. Three dozen male humans had been raised from infancy, educated and militarily trained to serve as a pool of candidates for bonding with the Wrath homunculus. Of those, only Bradley had proven strong enough. All the others had died, some in the initial attempt and the rest today, destroyed by the power of the Philosopher's Stone. The human lives were of no consequence, of course, but they represented an investment of time and resources that could not be recouped. Father needed Wrath to continue serving as the political and military leader of the puppet nation of Amestris, and for that, a human host was necessary. Another would have to be located quickly.

The new host would have to be someone whose will was strong enough to survive the process of bonding with a Philosopher's Stone. Someone for whom wrath was already a familiar emotion. Who was motivated and shaped by the desire for power. And who had sufficient status within the Amestrian military to make succession to its leadership seem plausible.

Father's deliberations were interrupted when Pride, the oldest and most powerful of his children, entered his chamber. "We've just received word that there are intruders in Laboratory 3," said the homunculus, whose appearance was that of a young boy surrounded by tentacles made of shadows. "It's the Flame Alchemist, with a small group of subordinates. I've sent Lust to deal with them."

The timing was fortunate. The Flame Alchemist would make an excellent host, if he survived. "Bring him to me at once," Father ordered. "Alive."

"Yes, Father," replied Pride. "And his companions?"

"They may prove useful in the future. Throw them out, but leave them unharmed."

"Your timing could have been better, Pride," grumbled Lust. The homunculus in the form of a shapely young woman had just finished mortally wounding the Flame Alchemist, better known as Colonel Roy Mustang, and one of his subordinates, Lieutenant Jean Havoc. Both men were slowly bleeding to death at her feet, although Mustang was still struggling to get up, calling to Havoc and hurling a string of threats and curses at her.

"You've made a mess," snapped Pride. He and Envy had found Lust in the main examination room of Laboratory 3, which was littered with burned debris from a recent explosion, including cooked fat and ashes from previous versions of Lust's body.

"Had some trouble, Lust?" teased Envy. "Looks like they forced you to regenerate your entire body at least twice."

"The Flame Alchemist was very annoying," she concurred.

"Try not to be so sloppy," Pride scolded. He noted that Mustang had stopped struggling and gone quiet—too quiet. Using his shadow appendages, the homunculus grabbed the man's wrists and forced his hands into view. The ignition gloves that the alchemist used to create his flames were in shreds, but in his right hand he clutched a piece of metal debris, which he had been quietly using to carve a transmutation circle onto the back of his left hand. He also held a lighter, which Pride forced him to drop.

"I'm coming after you next, freak," the alchemist threatened with a smirk.

"Pathetic," hissed Pride. "You creatures never stop your pointless flailing." A shadow wound its way around Mustang's neck and squeezed him into unconsciousness, then unceremoniously dropped him.

"Envy, take the Flame Alchemist to Father," Pride ordered. He pointed to Havoc. "Lust, take that one to Dr. Marcoh and have him healed, then turn him loose. I will deal with the other intruders." He headed for the door.

Lust sighed in annoyance and picked up Havoc's unconscious form, as easily as a human would lift a doll. Admittedly, killing him would have been a waste of a handsome plaything. She had gone on several dates with this human as part of an information-gathering assignment, but she had not been able to take him to bed, since the ouroboros markings on her body would have revealed her as a homunculus. It had been quite frustrating—something she decided to remedy as soon as he was healed. Her lips curved into a smile. He probably wouldn't like it, but surely that wouldn't fall under the definition of "harm," now would it?

"Great," Envy was grumbling, as he lifted Mustang with obvious distaste. "We get stuck with the grunt work, as usual." He attempted to sling the alchemist's limp form over his shoulders. While the weight of a human was no issue for Envy either, the body was too bulky to settle comfortably on his slight frame. Unique among the homunculi, he had the ability to change his entire appearance, but his usual form resembled that of a young male teenager. Now he transformed himself into a copy of Major Alex Armstrong, a particularly large, muscular, and shirtless Amestrian solider. "Much better," he grinned, balancing the body playfully on his shoulders.

"Stop screwing around, Envy," Pride snapped, pausing by the door. "And Lust," he added, "you're to turn that human loose immediately after he's healed."

Lust's face fell. "Spoilsport," she muttered.

Mustang woke up in the dark. He immediately tried to sit up, but couldn't move—something was holding him down. Restraints, he saw through the dimness, strapped over his shoulders, stomach, and legs, binding him tightly in place. He was lying on some kind of bed.

He surveyed his surroundings. It was a large, windowless room, possibly underground, and barely lit. The ceiling, walls and floors were covered with a large number of pipes, leading to a central location that he couldn't see from his restrained position. Then his eyes made out the figure of Major Armstrong standing off to one side, watching him with an uncharacteristically bored expression.

"Armstrong?" he exclaimed. "What are you—" The large man glowed and began to change, shrinking in size and taking on the form of a young man with spiky black hair, an ouroboros tattoo on his left thigh. "Oh," said Mustang. "You're one of them." The figure snickered.

So they had a homunculus who could copy people. That meant the enemy could be anyone, anywhere, he realized with a sinking feeling. Of course they had been caught. They had been woefully outgunned from the beginning, and he had walked his subordinates right into a trap. "Where is Havoc?" he demanded angrily. "Is he all right?" He didn't dare mention Hawkeye or Alphonse, hoping they had escaped undetected. The homunculus continued to snicker, but did not reply.

Mustang had been badly wounded, skewered through the ribs by Lust's blade-like fingernails, along with other injuries. But now he felt no pain at all. He craned his neck until he could see the back of his left hand, where in desperation he had tried to carve a flame alchemy array into his skin. Now the wound was gone, the skin unbroken. They had healed him completely—how? And more importantly, why?

An older man with glasses and a mustache approached, wearing a doctor's coat, and turned on a utility lamp over Mustang's head. Now it was much too bright, and he squinted painfully at the light shining in his eyes. The doctor began prodding at him, murmuring, "Yes, this specimen is in good shape, and still fairly young. He has a good chance." He broke into a grin, revealing a gold-capped front tooth.

"A good chance for what, exactly?" Mustang asked, now even more alarmed.

"Surviving," leered the doctor.

The next to approach was a tall, strange, middle-aged man with long blond hair and a beard, wearing a long white robe. This man was definitely in charge; he moved slowly, with an imposing air, and both the doctor and the homunculus immediately deferred to him. "It is ready?" the man asked, inclining his head toward Mustang, his voice deep and ponderous. "Yes, my lord," responded the doctor.

The blond man stood absolutely still, but his forehead began to glow. As Mustang watched in horror, a crevice slowly opened within the glow, revealing a structure that looked like an eye turned sideways. It began to drip a red substance, which congealed into a blob; when it had reached about the size of large grape, the blob rolled down the man's face, then fell into his outstretched palm.

He turned and presented his hand to the doctor, who carefully scooped the red substance into the mouth of a large syringe. The doctor's expression was reverential, his hands shaking slightly as if with excitement, as he finished assembling the syringe. Mustang swallowed. He had a terrible feeling that whatever that red substance was, they were about to inject him with it.

"What the hell is that?" he exclaimed, struggling futilely inside the restraints. "What are you doing?"

The doctor began swabbing the inside of Mustang's right arm with alcohol. "This is the Philosopher's Stone," he grinned. "Isn't it wonderful?" And with no further explanation, he jammed the needle into Mustang's vein.

The pain was like nothing Mustang had ever felt. He seized, and his whole body went rigid, as the substance—whatever it was—coursed through him, invading his entire body. It felt as if acid were running through his veins. He would have screamed in pain if he had been physically able; instead he could only gasp and gurgle as his lungs desperately fought for air. Blackness gripped him as his mind began to warp in out of consciousness. His last coherent thoughts were of the subordinates he had brought with him into Laboratory 3: Please let them have escaped this.

Amid the agony, he was dimly aware of the blond man peering down over the bed, with a coldly curious gaze that a boy might use to examine an insect. "Will you be the one to accept my wrath?" he intoned. The voice was growing fainter, the image farther away, as if Mustang were falling away from it. "Or will it be someone else…"

Sometime much later, Mustang felt himself gradually returning to consciousness.

"…an even better specimen than Bradley. He's recovered in less than half the time," the gold-tooth doctor's voice was saying. Mustang opened his eyes, saw that he was addressing the blond man. Father, Mustang remembered hazily.

"Even the Ultimate Eye—it's on the right side this time—formed without destroying the original. The iris is hidden, but intact," the doctor continued. He looked over and noticed that Mustang was watching him. "Good. You're awake. How do you feel?"

The haze of the ordeal was fading, and he felt a new energy coursing through his body. "I'm fine. Untie me," he scowled. Now he knew where he was. Father's chamber. Of course he was here; he belonged here.

The doctor unbuckled the restraints, and Mustang sat up. No. Not Mustang, not anymore. Not entirely. My name is Wrath.

"Welcome back, Wrath," said the spiky-haired youth. Envy. "Nice job getting yourself killed, by the way—"

"Silence," ordered Father, and Envy obeyed, albeit with a sour expression. Father strode over to Wrath's bed and circled him, scrutinizing him intently. "You have accepted my Wrath. Are your memories intact?"

"Yes," Wrath responded. "And the memories from this new body, too. It may take some time to sort them out."

"It will not interfere with your duties." A statement, not a question.

"Of course not, Father." Wrath stood up, drawing a deep breath into his new lungs, and gave a perfunctory bow. "I'm ready to resume leading this country, as soon as everything is in place."

"Pride is making the arrangements. We will wait for him to return. Doctor, you are dismissed." The gold-toothed man bowed his head briefly and exited the room without a word. Father continued standing, but his gaze wandered off somewhere into the empty air, lost in contemplation of some deeper matter that Wrath could only guess at. And with that, they waited.

Envy, feeling quite forgotten, had retreated to a corner to sulk. Newly-formed homunculi always soaked up more than their fair share of Father's attention. And what was he supposed to do with himself while they waited for Pride? He was already bored.

After awhile he noticed that Wrath was eyeing him intently, wearing a thin smile. "What?" asked Envy, annoyed.

"You're the one who killed Maes Hughes."

"Who?" he scoffed. "Wait—that imbecile in the phone booth? Why do you care about that?"

Wrath shrugged. "I don't. But it was quite the obsession for my human host. They were friends, and he swore that he would find the murderer and take revenge. His first experience with genuine wrath." He was still wearing that unnerving smile. "It probably made this bonding possible, in fact."

"You're welcome," snapped Envy. He had never liked Wrath, didn't consider him a true member of their family. None of the other homunculi did either. A body that aged and couldn't regenerate, living with a woman that he picked for himself, and that creepy fake cheerfulness. Wrath was just too…human.

Pride chose that moment to return. "Everything has been arranged," he said to Father as he strode into the chamber. He turned to address Wrath. "Bradley has left a will, appointing you as his successor to the Führer Presidency. He has also left you title to his estate, and guardianship of his son." He smiled ironically.

"Understood," said Wrath. "And my subordinates? There were two others in Laboratory 3, besides the injured one who was with me. Where are they now?"

"They've been released unharmed. The injured one was healed. You can continue to use them as you see fit," Pride responded.

Wrath nodded with satisfaction, then turned to Father. "I presume that, as before, I'll be permitted to choose my own wife?"

"Such trivial matters do not interest me," Father intoned. "Make your own arrangements." He turned his back on the homunculi and strode back to his throne.

"Excellent," Wrath replied with a smirk. "I have just the woman in mind."