Full story summary: He helped lead the rebellion that ultimately drove the false gods from the Earth and bury the Stargate, but he was too late to save the Pharaoh, his cousin and best friend. Death would have been a relief, a reward. So he lived on, alone.

5000 years later, SG-1, with the help of Jacob Carter and the Tok'ra Selmak, raid the cult compound run by the Goa'uld Seth. They didn't count on finding another Goa'uld with no love for the System Lords, particularly those who steal identities.

Chapter summary: In which Pegasus knows, Seto stresses, and Yugi asks for help.

The Serpent's Vow

1: Game Start

Pegasus knew. There wasn't much Seto could do about that. On the bright side, as rich and influential as Pegasus was, no one would ever believe something so obviously outlandish. Literally. At least the megalomaniac knew when to keep his mouth shut. For now anyway. It had taken years for Seto to manufacture his current identity and, despite how hard it was for him to admit it, even to himself, he'd grown rather fond of it.

Kaiba Seto. Adopted son of Kaiba Gozaburo, former CEO of Kaiba Corporations, formerly one of the world leaders in weapons manufacturing. It had taken a long time for Seto to wrest full control of KaibaCorp from the money and warmongering idiots of the Board and focus his energies on something less bloodthirsty and more beneficial. Games.

Perhaps it was his sentimentality. Perhaps it was just logical. Maybe it was a combination of both to varying degrees depending on the time of day or night. After all, war was just as much a game as chess. The games pieces just bled and died instead of topple over onto the board in defeat.

But this was no defeat. Finally, Seto had succeeded. The child he'd come to adore as the brother he never had but always wanted would have a secure future. Seto knew from experience that eventually people would start to get suspicious of his continued youthful appearance. Especially when compared to young Mokuba's relatively rapid growth. Hopefully, it would be a dozen or so years before that happened and he was forced the vanish yet again.

He had to stop typing and press his mouth against his folded hands, glaring at the glowing computer screen in an attempt to will away the pain that threatened to drown him in despair. Mokuba. Never in all his many long years did Seto ever think he would latch onto someone so thoroughly again. Blue eyes the shade of glacial ice slipped to the small form slumbering away on the bed next him, curled up in his white trenchcoat and a pile of pillows.

If Seto had a weakness, it was his vulnerable heart. He felt everything so intensely it often left him raw and exposed. Damn it to Osiris, Seto loved Mokuba like he'd once loved his pharaoh. Love, loyalty, absolute trust. All things he never thought he would ever have or be worthy of ever again.

Long ago, he betrayed his Pharaoh. Whether he did so willingly or not didn't matter. The betrayal still resulted in harm and opened the door to his beloved cousin suffering a fate worse than death. Alone. Seto could never forgive himself for that. Death would have been a mercy.

So he lived.

It had been a long time. Almost too long.

He couldn't bring himself to leave this host. It was his in every single way that mattered. He'd been implanted when both he and his host were too young to remember or have a solid sense of self. The only consciousness to ever fully exist in this body was his own. He was Seto. He couldn't handle the idea of abandoning what he saw as himself and possessing some other innocent person and wearing them like a new costume. The very thought sickened him.

Unfortunately, over time, his many years of lonely existence and exposure to the sarcophagus, even with the numerous alterations he's made to the device, had begun to degrade his mind and personality. When he finally realized what was happening to him, it was almost too late. He destroyed the sarcophagus as completely as possible and swore he would never risk using any Goa'uld device like it again. Not unless he had no other choice.

The resulting withdrawal symptoms that plagued his body also wreaked havoc on his psyche. When Mokuba found him crumbled on the ground that fateful day, Seto had been conscious but barely sane. He latched onto the boy with the possessive single-mindedness of a hostless Goa'uld and, for once, he didn't feel ashamed. Mokuba was worth everything Seto could give. He would do anything to make sure his precious little brother would be protected.

No matter what the cost.

Which led him back to the problem of Pegasus. Pegasus J. Crawford was certifiably insane and a megalomaniac the likes of which any Goa'uld Seto knew of would be proud to call enemy. The fact the American businessman had the Millennium Eye just made matters worse. Pegasus didn't just suspect, Pegasus knew what Seto was. He'd seen Seto's true self buried beneath layers of skin, muscle, mind, and soul. Pegasus knew and he was demanding answers.

For a man still recovering in the hospital and reeling from a devastating loss at the hands of a boy, Pharaoh reborn though he may be, Pegasus was certainly pushy. The damning email Seto was trying hard to formulate a decent reply to spelled out everything. How was Seto supposed to explain this in a way that didn't make him seem equally insane? By all rights, he shouldn't have to. Pegasus had been the one to invade his mind in the first place. None of this would have happened if he hadn't panicked when Pegasus' goons broke into his home and threatened him. He'd still been fresh from a Penalty Game induced coma. He was hardly in a position to defend himself let alone think straight. All he could think about clearly was surviving long enough to get Mokuba back.

But Pegasus was smart. He knew when and where to pry to get what he wanted. Had this been a business venture, Seto would have met it head-on. But this was personal. The Pharaoh he once served knew Seto's true nature. Mokuba however... Seto adored his little brother. But if Mokuba was faced with indisputable facts proving his big brother was 'being controlled' by a snake in his head, Seto would lose him. He couldn't bear that. He was always losing what mattered most. Not now. Not anymore. Not if there was anything he could do to stop it.

The only question now was how? He ran his fingers through his brown hair as he silently stressed. Damn that man to Ammit's gullet.

Seto could tolerate his loss to Pegasus only because the ditsy necrophiliac had the Millennium Eye. Now, whether the man still had it or not after the Duelist Kingdom fiasco was another question entirely. Although Seto was beginning to doubt it if the rumors of Pegasus spending time in the hospital for a facial injury were true.

Yugi knew, but he hadn't told Seto outright and Seto wasn't going to ask. As difficult as it was to admit, Seto wasn't a part of his Pharaoh's closest circle this time around. Granted, they hadn't met under the best circumstances so while it gnawed at him, it made sense.

Seto had barely been sane when he faced off with Yugi the first time. His Shadows, reacting to his lack of self-control and damaged psyche, lashed out at Yugi's Grandpa. It had been so easy he'd barely realized he'd done it. The fragile shell of sanity he clung to had been degraded by the sarcophagus withdrawal and Gozaburo's constant abuse until Seto hardly recognized himself. He'd been... He had almost become...

The Shadow Game Yugi had subjected him to at the end of their Shadow Duel managed to thoroughly remove any lingering hold the sarcophagus had on his mind. It also shattered everything Gozaburo had hammered into his head while he'd been… compromised. Forced to rebuild his sense of self from scratch, Seto chose to focus his everything on Mokuba, his beloved dragons, and Yugi.

Pharaoh. Yugi was the Pharaoh reborn. His Pharaoh. Seto knew it. He could feel the oaths he'd sworn so long ago, witnessed and bound by the Shadows, throb with the knowledge. Yugi was alive and he'd solved the Millennium Puzzle. Finally. After so many years.

Why had it taken so Ra-begotten long for him to return?!

During that time, Seto had been alone. He'd entrusted the Millennium Items to High Priestess Isis and her descendants to protect, keeping the Rod for himself. Unless Pegasus was one of Isis' descendants, which was ludicrous, then the Tomb Keepers apparently failed in their duties somewhere along the line. The Pharaoh had his Puzzle, Seto had his Rod, Pegasus may or may not still have the Eye, and someone else in Duelist Kingdom had another Item. Seto remembered sensing the Item, but not clearly enough to identify which one it was or who wielded it. That left three Items unaccounted for. Not good news.

He bit back a grimace as he dropped his gaze to his Deck sitting still and innocuous on his desk by his mouse. He could feel the Shadows pulsing within them like a beating heart. He could feel her within them. She didn't judge him or lecture him or fear him. She just loved him. Finding Mokuba had been the start of his mental and emotional healing. Finding Kisara again -in a card game of all things- should have been his first clue that his long wait was finally -finally!- over. Finding Yugi...

He should have recognized him by sight if nothing else. The Millennium Puzzle was a raging sun in the darkness of the Shadow Realm. He'd just been too blinded by his own despair to see it. Too lost in his muddled mind to believe that the person he'd sworn himself to mind, body, and soul... that the person he had loved and betrayed was alive again.

Now he was fully aware and utterly terrified. His Pharaoh knew what he was. It wasn't easy to keep something like that secret after his betrayal. But Yugi... Yugi was like Mokuba. He didn't know the truth. Yugi didn't know anything. In fact, Seto was willing to bet everything he had that Yugi hardly remembered anything from his past life.

Five thousand years was a long time, no matter how much of it Seto slept through. Seto could only wonder how the Millennium Puzzle found its way to and be solved by someone who looked exactly like his beloved Pharaoh. He hoped... He prayed to the True Gods that Yugi would remember soon, and that he wouldn't despise Seto simply because he was something despicable.

For now, there was hope and that was enough. Each time Yugi extended a hand in friendship, Seto felt another sliver of ice melt away from his heart. One day he would take that hand like he had so many eons ago and learn to trust again. This time, hopefully, he wouldn't be too late.

A loud buzzing sound abruptly shocked him out of his thoughts. His computer had gone to sleep at some point, the screen with its incriminating email now black and lifeless. Thankfully, a password and facial recognition were required to open the device, but Seto wouldn't put it past Mokuba to figure out a work around. Still, Seto didn't realize how long he'd been oblivious. He was losing his edge.

Obelisk support him.

Rubbing his face in mounting aggravation, he glanced over to his right. The light from the full moon shining through his hotel room window was bright enough for him to see the device responsible for the offensive noise without the need for a lamp. Swiping the cell phone from the glass and steel surface, Seto answered it without bothering to check the caller ID

"This had better be good," he growled, shutting his laptop quickly, "because if you woke Mokuba, I will kill you."

A snort. "Ah, sorry."

"Pha- Yugi!" Seto gasped. Biting his tongue, he took a deep breath to quell his edgy temper. "Hold on," he muttered.

Standing, he brushed Mokuba's hair tenderly and made his way to the sliding glass door and stepped out onto the balcony. This high up, most of the city noise was muffled by the night air. He could smell the coming rain and feel the breeze on his face. Sliding the door shut quickly and quietly behind him, he tapped his hands-free earpiece.

"Can you hear me?" he asked.

"Yes. Why?"

"Nothing." He tucked his phone in his pocket and leaned over so his forearms rested on the cast iron railing overlooking the Puget Sound. "What is it, Yugi?"

"I… How are you doing?"

"Fine," he said, trying to keep his voice calm.

"You sound tired."

Damn. "Jet lag."

"After a week?"

He sighed in mounting annoyance. "Was there a point to this call?" he grumbled. "You never call this late unless it's something important. You never call ever unless it's something important."

His Pharaoh's silence was telling. "Kaiba, I need your help."

Of course. A small part of his mind that desperately wanted his cousin back keened with glee and worry. Yugi, his Pharaoh, was coming to him for help. Yugi came to him, of his own free will. It was both thrilling and terrifying. Yugi's ability to attract trouble was, quite frankly, astonishing. Thank Ra Seto was good at cleaning up other people's messes.

"What are you caught up in this time?" Seto said, twining his fingers together thoughtfully as he watched the lights from a ship in the harbor move across the water. He swore, if someone else was trying to steal the Pharaoh's Puzzle, Seto would personally rip them to shreds. Having his soul ripped out, again, tended to have that affect on him.

"It's not me," Yugi said hesitantly.

Oh no. Please don't be the mutt.

"It's Honda."

…motorcycle boy?

"What about him?" Seto asked, confused but mildly interested. "The convention isn't supposed to end until Sunday. If you can't find him, then he's probably-"

"I know where he is, Kaiba," Yugi said urgently, "I just can't get to him."

Deep breath. "What aren't you telling me?" Seto said.

"He's been taken," Yugi said. "I don't really know how to explain it. He was fine and then he just walked away and left with them and-"

Kidnapped then. Great. How Yugi and his geek squad managed to constantly find themselves in ridiculous situations like this was beyond Seto's comprehension.

"-Jounouchi and I" -oh Ra, the mutt was involved too- "found out where he was taken but we can't get in. Not without being shot."

Seto stilled. Guns? "What do you mean 'shot'?" he said, keeping a strict hold on his temper when he felt his Shadows begin to curl around his wrists in response to his emotions.

"They have guns," Yugi said. "A lot of guns. Some of them are military grade."

Which meant this was most likely an organized hit. Shit. Seto pinched the bridge of his nose as he processed this. "Where is-" He stopped. There that music in the background. It was faint but distinct. ...He recognized that music. "Yugi," he said slowly, "I'm going to ask you one simple question and I want you to answer me honestly. I will know if you lie. Where are you right now?"

Silence followed by a heavy sigh. "At your hotel. In the lobby."

Seto sighed.

"Please, Kaiba," Yugi pleaded. "I wouldn't have come to you if I didn't think you could help."

That… strangely hurt, even though he probably deserved it.

"Fifteenth flour," Seto said into the wireless speaker. "Room 1513. Don't knock. You'll wake Mokuba. I'll know when you're here."

"Thank you."

Straightening, Seto tapped the railing. "Is there anything I should be looking into while you're on your way up?" he asked.

"Have you heard of someone named Seth Fargough?"

"No." His eyes flashed gold. "But I will."

A/N: Finally have some downtime after a crazy, hectic few weeks. I've had the idea of Kaiba being a Goa'uld for a while now but never got around to figuring out how that would work out. Then I watched the Stargate SG-1 episode "Seth" and the idea sucker punched me in the face. We'll see where this goes.

This is not related to the Shadow Justice series. I may write a SG-1 crossover for that one later one. But this fic is a standalone.