This is an idea that's been cooking in my head ever since I saw the end of the Flash episode S1E17 "Tricksters" (which was an awesome episode!);
Spoiler alert: we see that Arrow, Flash, ATOM and Firestorm (at the very least) will team up at some point, so I figured, if the heroes are going to work together, then so would the villains.
Anyway, this little one-shot is based off that idea, and it takes place after the above episode and during the Arrow episode S3E18, so without further ado...
Nanda Parbat
In the highest room of the monastary-like sturcture that was the home to the League of Assassins, the Head of the Demon sat bathing in his chamber. As Ra's al Ghul allowed the healing waters of the Lazarus Pit to rejuvenate his body, he thought back to the events of the previous months.
Oliver Queen had challenged Ra's to a duel over the death of Sara Lance, his daughter's beloved. Neither Nyssa nor Ra's had believed his claim that he was the one who murdered Sara, and they were later proven correct in their beliefs, when Oliver's sister Thea, gave them Sara's true killer; Malcolm Merlyn.
Of course, at the time, the Demon's Head had to accept Queen's challenge, and bested the young man in a duel that should have killed him. However, the Arrow returned to Starling City, revealing to the League that Oliver had survived his ordeal.
Nyssa had been livid at the Arrow's survival. The Demon's Head, on the other hand, had realized that he had found his worthy successor. Ra's emerged from the pool and put his clothes back on, noticing that healing powers of the Lazarus Pit were slowly beginning to have a diminishing effect on his body.
He needed a worthy heir, and when Oliver returned to Nanda Parbat to rescue Malcolm Merlyn, Ra's had given him the offer of a lifetime, even releasing Merlyn and Queen's companion, John Diggle, as a gesture of goodwill.
Nyssa had been upset when she learned that she was no longer considered to be the Heir to the Demon, but her father knew that she had let Sara's death cloud her emotions, whereas Oliver Queen possessed the strength and willpower to lead the League of Assassins.
He would become the next Ra's al Ghul, no matter what.
Of course, Oliver Queen had refused Ra's proposal, a disappointing but not unexpected outcome. Which was why Ra's and the League had started killing criminals in Starling City, to turn the police against the Arrow and forcing him to accept this generous offer.
Currently, the League had outed the Arrow's identity to the police, forcing Oliver into running. In time, Maseo would bring the report that Queen had chosen to follow the prophecy that had been foretold.
Heading to his training room, Ra's al Ghul began a light training exercise between himself and six of his assassins. Two of them had fallen when Ra's brought an abrupt end to the fighting, raising his hand in an order for his assassins to stand down.
He heard a disturbance emanating through his home, as loud crashes, and occasional grunts and screaming permeated through the still silence of the monastery. Two seconds later, the door to the training hall burst open as one of the guards was hurled through the entrance, coming to a halt at Ra's' feet.
The remaining four assassins turned to protect their master, but were quickly cut down in less than a second by a yellow blur with red lightning trailing it. Soon, Ra's was standing among his fallen disciples, dead of either broken necks, blunt force trauma or stab wounds.
The assailant then chose to make himself known, coming to a halt in front of the Demon's Head, allowing Ra's to get a good look at his visitor. The first aspect that stood out was the strange yellow costume that covered the man in head to toe. Glowing red eyes emerged from behind his mask, while the rest of his face and body was vibrating at an inhuman pace, preventing any details from being visible.
The two men sized each other up for a moment before the man in yellow started speaking.
"So, you are the great Ra's al Ghul. The Head of the Demon and the leader of the League of Assassins. The man that history textbooks said was the most dangerous human on the planet."
Even the man's voice sounded inhuman and demonic, no doubt caused by the vibrations of his body. Despite that, Ra's could tell that the man in yellow sounded unimpressed and condescending.
"Somehow, I expected more." Ra's himself looked unimpressed and calm about the man in front of him, before he turned away to grab a drink.
"Well, you have me at a disadvantage. You know who I am, and yet I don't know your name." The man in yellow tilted his head to the side, as Ra's addressed him while his back was turned.
"You can call me... the Reverse-Flash." Something in Ra's memory clicked, and he turned back to his visitor.
"I'm assuming you have something to do with this 'Flash' that has appeared in Central City?"
"You might say that." The Reverse-Flash responded, "Just as I might assume that you're responsible for unveiling the Arrow's identity. And I think we can help each other."
At that moment, several assassins appeared behind the Reverse-Flash, garbed in their traditional costumes and wielding bows and arrows, all of which were pointed at the yellow costumed man. Before anything else happened, Ra's ordered his disciples to leave the two of them alone.
"I'm listening." He said, curiousity in his eyes.
"I believe we have a few common enemies. I understand that you desire Oliver Queen for your own purposes. I have a similar use for the Flash."
"And your offer is?" Ra's asked. The glowing eyes looked at him.
"You keep the Arrow from interfering in Central City, and I'll ensure the Flash will be preoccupied and unable to assist Mr. Queen against your machinations."
"That seems rather reasonable." The Demon's Head replied, "But if you're this powerful, why do you need my help? Or the Flash, for that matter?"
"That is not your concern." Reverse-Flash growled, as he disappeared and reappeared less than a foot from Ra's in the blink of an eye. Ra's didn't flinch at the sudden movement.
"Do we have a deal?" The demonic voice ground out. Ra's pondered for a moment before making up his mind.
"We'll have to discuss the finer points of this later," The Demon's Head admitted, "But I will accept your offer, for now."
Ra's offered to shake his hand, but the man in yellow didn't move. After a moment, he put his hand down, seeing as Reverse-Flash wouldn't budge. 'He needs to work on his manners.' Ra's thought, before saying out loud;
"Well, can I offer you a drink, at least?" He said holding up a glass. Again, his visitor said nothing. "Very well." Ra's sighed, "I must insist though, that the next time you come here, you could at least knock first."
"I'll keep that in mind." Even through the demonic tones, Ra's could hear the heavy sarcastic underline. The Reverse-Flash turned to leave when a question from Ra's stopped him in his tracks.
"Before you leave, I must know how you expect me to contact you?" Turning his head over his shoulder, allowing Ra's to glimpse one of his glowing red eyes.
"I'll find you." Reverse-Flash said, with the subtle threat not lost on Ra's.
And with that, the Reverse-Flash disappeared in a yellow and red blur, leaving the mountains and the monastary far behind. Ra's watched as the monstrous metahuman disappeared, and looked around. To most normal people, this would be a horrifying experience. To Ra's al Ghul, it was an ordinary day.
I hope everyone enjoyed this, and seriously, I cannot wait for the next episodes of the Flash and Arrow. EDIT: It's especially funny that the Flash did this exact same thing during the Arrow Season 3 finale, and took out all the assassins in the monastary in under a minute.
Reviews are welcome.