The Outbreak was a terrorist attack on Starling City by the League of Assassins led by Ra's al Ghul in his quest to make Oliver Queen his heir. It was foiled by the combined efforts of Team Arrow, Malcolm Merlyn, and Palmer Technologies.
Sara Lance's death
In October 2014, Sara Lance returned to Starling City on a mission for the League of Assassins to track down Malcolm Merlyn. While searching for Malcolm, Sara also looked for Ken Zhi Jansen, who was connected to the former. However, Sara was confronted and killed by Thea Queen, who had been drugged by Malcolm with Vitura. Knowing the League would mark Thea for death, Malcolm used this as leverage against her brother, Oliver Queen, and Team Arrow to settle his blood debt with Ra's al Ghul.
Hunting Sara's killer
Upon Sara's disappearance, Nyssa stormed into the Arrowcave, aiming an arrow at Oliver. Oliver informed her of Sara's death. Shocked and heartbroken, Nyssa revealed that Malcolm was still alive and that Sara had come to Starling City to trace a rumor that he was here. Nyssa visited Sara's grave, where she encountered Laurel. Nyssa swore a blood oath to avenge Sara's killer using the words "أقسم بحياتي". Nyssa went to Sara's safe house and began to cry when she noticed Oliver behind her. She and Oliver found pictures and notes Sara had made while investigating Malcolm. Team Arrow and Nyssa found out Merlyn was hiding in a Buddhist temple. Infiltrating the temple, Nyssa confronted the leader who was meditating. Realizing it was Malcolm as the leader passed away years ago, Nyssa tried to kill him but Malcolm incapacitated her and fled the scene, though Oliver managed to put a tracker on him. Nyssa was angry at Oliver that he did not attempt to kill Malcolm.
Nyssa was furious upon learning Oliver had talked to Malcolm and did not believe he killed Sara. After learning Thea was actually Malcolm's daughter, Nyssa kidnapped her as bait to lure Malcolm to her. Oliver freed Thea and started to fight Nyssa. Malcolm later showed up and soon managed to overpower Nyssa. Malcolm swore to Nyssa that he did not kill Sara and suspected her own father to be the killer. Oliver remained firm with Nyssa that he wouldn't kill Malcolm or allow the League to come near him, much to Nyssa's anger.
Before leaving the city, Nyssa talked with Laurel, whom she encouraged to train and become stronger.
After returning to Nanda Parbat, Nyssa reported what happened to her father, who assured her that Malcolm would face justice. However, Nyssa appeared to have doubts regarding Malcolm's guilt in Sara's death, especially when her father stated that Sara "was never truly one of us". Upon hearing of Oliver's decision to protect Malcolm, Ra's declared war on him.
Nyssa later confronted her father about Oliver being still alive. Ra's was aware of this and stated he also knew that Oliver did not kill Sara. Nyssa questions if he ever approved of her relationship with Sara. He said he knew their love would only end in heartbreak. Nyssa mentioned that even if Oliver did not kill Sara he still deserves to die for defying her father. Nyssa and a group of assassins went to Starling City as they looked for Malcolm Merlyn, they got contacted by Thea who offers them Malcolm Merlyn in return for safety. Nyssa agreed and Thea tells them where Malcolm is. Nyssa and her team find Malcolm as he is getting attacked by Laurel. He easily fend her off and took her baton, after which she pulled a gun on him. Her assassins quickly disarmed Laurel and surrounded Malcolm. Nyssa faced Malcolm in a duel while she used her scimitar and he used the baton of Laurel. After a short fight she managed to overpower him and knocked him out. Preparing to leave by helicopter Nyssa told Malcolm he would suffer for what he did. Malcolm replied that her father only wanted to punish him for the undertaking and the he never cared for Sara. Malcolm said her love for Sara made her unable to take the place of her father. Oliver Queen came to his rescue. Nyssa ordered her men to leave with Malcolm while she prepared to hold Oliver off. She fought Oliver however he managed to tie her up with a trick arrow and capture her. As the helicopter flew Malcolm away she mentioned to Oliver that Malcolm will never be seen again.
Nyssa got locked up in a cage in the Arrowcave. She spend her time meditating as Oliver and his team discussed what to do. Oliver send the rest away as he asked her where Nanda Parbat is. Nyssa explained that every action of him had frustrated the vengeance for the death of Sara, and she tells him the location as she is certain he will die there. Laurel later brought her water and Nyssa said Malcolm will get tortured by her father, but Laurel does not seem please how the killer will be punished. Laurel said she hated Merlyn and that he was like a piece of Sara that still existed. However now he is gone she can not even remember the sound of Sara her laugh. Nyssa told her that the first time Sara was brought to her father she was the witness of a demonstration of his power, however she simply laughed as she was completely innocent. It was that moment Nyssa fell in love with her. A touched Laurel thanks her for sharing this. Thea later visited her at her cage as she explains she can not live with the guilt of what she did. Thea explained to Nyssa that she lied to her and that she was the one who killed Sara. Thea then opened the cage door and hands Nyssa her scimitar as she says she can have her revenge.
Nyssa took the scimitar but refused to kill Thea. A frustrated Thea explained how she killed Sara while being drugged. Nyssa said that the murder will be revenged with the death of Malcolm. Laurel and Roy came in and attacked Nyssa as they believed she had escaped. Nyssa knocked them both down but was shot with an anesthetic and passed out. Locked up in the cage she was surprised when Oliver returned and set her free. She demanded explanation as she refused to believe her father had let Malcolm go. Oliver told her to just go home.
When she arrived at Nanda Parbat, her father said coldly he was happy to see her again. She demanded to know why he had let Malcolm go. Her father explained it was a favor to Oliver as he would become his heir. Nyssa said it was because he did not approve her relationship with Sara. Her father explained how she was unfit to be his heir as she had allowed weakness to come into her life which had made her emotional in her judgement. Nyssa attempted to kill him with a sword strike which he easily blocked. Nyssa said she would not watch her legacy being given to an outsider and left.
Sometime after Murmur's arrest, Ra's arrives in Starling City dressed as the Arrow, and quickly killed Murmur's remaining men leaving only one alive to spread the word. To force Oliver to take his offer he made Maseo and other assassins dress up as The Arrow and kill criminals.
After Maseo killed Celia Castle and failed to kill Felicity Smoak, he met with Oliver and told him to accept the title of heir to the demon or he would spend the rest of his life in a cage, claiming he wasn't going to capture Oliver when he challenged it but a police helicopter soon arrived. He later sent Maseo to intercept and capture Captain Lance and brought him to Ra's where he revealed The Arrow's identity as Oliver Queen.
Oliver Queen got arrested but got free when Roy turned himself in as The Arrow to set Oliver free. After Roy faked his death, Ra's targeted Thea. He appeared in her apartment and asked her if she knew who he was. After she said Oliver would kill him, he said Oliver would beg him to become the next Demon's Head. He caught the knife Thea threw at him and the two got into a fight. Ra's effortlessly dodged her strikes after which he slammed her through a table. Drawing his sword, he then impaled her, and said a quick prayer, after which he left the apartment.
Ra's greeted Oliver with his entire league as a desperate Oliver arrived at Nanda Parbat holding a deceased Thea. After Thea's resurrection, Ra's expected Oliver to hold his end of the deal. Later, an upset Felicity approached Ra's and told him she doesn't care about the prophecy. Felicity told Ra's he didn't know what love was, though Ra's told Felicity about his past life. Ra's told Felicity he is offering a chance for Oliver to have a proper goodbye, one that he never had a chance to do. After a failed escape attempt by Felicity, Malcolm, and Diggle, Ra's asked Oliver who assisted them, though Sarab quickly came clean and revealed he killed three of the league members. Ra's told Sarab he won't punish him for Maseo's actions and spared him for his loyalty. Ra's went on to mark Oliver with a mark and started to cleanse Oliver of his personality so all that remained was Al Sah-him.
The next weeks Ra's personally trained Oliver and helped him improve his swordsmanship and combat skills. He used isolation and brainwashing techniques to make Oliver forget about his past and he began to accept his new identity and name. Exposing him to a herb Oliver started to hallucinate and believed a captured intruder was, in fact, his friend John Diggle. Ra's ordered him to kill him and Oliver quickly overpowered the intruder in a sword fight and killed him after which he realized the intruder was not John.
Impressed with the loyalty of Oliver Ra's showed him a few ruins as he told him he and Damien Darhk were like brothers and both candidates to become the new head of the demon. After Ra's was chosen he was ordered to kill Damien, however, he hesitated and Damien escaped and started his own organization called the H.I.V.E. Ra's explained to Oliver how Damien had attempted to buy the earthquake device and was responsible for multiple crimes. This was a direct result of Ra's having doubted in killing him. Ra's then told Oliver he does not want this for Oliver so he ordered Oliver to take out his rival for the title Heir of the Demon.
After Oliver captured Nyssa and brought her to Ra's, he complimented Oliver. He recalled how Nyssa used to steal food when she was young, but that she had never been able to hide things from her. He searched Nyssa her weapons and found the Omega virus. Ra's told her he would remember her as the warrior she once was, Nyssa replied that she was not afraid of him. Ra's ordered Oliver to kill her but stopped him at the last second. He mentioned Nyssa had been defeated by Oliver and was no longer a threat. He told both of them they would marry and Nyssa would become the bride of the demon.
Ra's explained to Oliver that the ruined village he had shown him was his former home. He mentioned that to become the new head of the demon one had to wipe out his former home. Just like he had did and the former Ra's before him had whipped out Alexandria. Ra's explained that he would unleash the Omega Virus on Starling City. Ra's recalled how Maseo had come to him and offered him the Alpha-Omega Virus when he wanted to join him. Maseo reported a plane had been readied to spread the virus.
Ra's visited Nyssa and explained to her how he had met his concubine Amina Raatko. He gave Nyssa a necklace he had given to her, and she then gave it to him to give it to Nyssa for her wedding day. Nyssa refused and Ra's told her she would marry Oliver or she would suffer the pain of a thousand deaths.
When John Diggle, Malcolm Merlyn, Laurel, Felicity, and Ray Palmer blew up his plane, a huge fight started in which Maseo and many assassins got killed. Ra's confronted them and made his men capture them. He explained to them the plane was just a distraction to see if there were any traitors reporting to them. Team Arrow made it appear like Maseo had been the traitor.
Ra's talked to Malcolm, who told him Oliver had been the one betraying him. Ra's called Oliver who told him that was not the case and he was devoted to the League. Ra's went to Team Arrow and threw in the Omega Virus as they screamed for Oliver to help. He and Oliver walked away as they left them to die.
Ra's, Oliver, Nyssa and a squad of assassins departed on a plane. Oliver woke up and Ra's told him there are dreams of desire, temptation, and truth. Oliver explained that he dreamed of rebirth as Head of the Demon. Ra's told him they would destroy Starling and then he would get the ring that would allow him to command the League. The plane started to shake and the pilot told them the plane had been sabotaged. Enraged Ra's blamed Nyssa. Oliver told him it was his doing. Oliver handed Nyssa a sword and she started to fight the assassins. Ra's mentioned to Oliver he had given him his holy mission. Oliver told him he had one already. The two fought and Ra's managed to knock down Oliver. Nyssa killed his assassins but Ra's subdued her and Oliver and promised them he would destroy the city and then hunt them forever. He then escaped from the crashing plane by parachute.
Ra's tracked down his rival Damien Darhk to a hotel in Starling. However, he had already escaped, and Ra's noticed Oliver and his team closing in on his assistant. Ra's called the assistant and then shot him. He taunted Oliver and told him he would spread the virus and destroy the city.
Ra's then unleashed the Alpha-Omega on Starling City by means of four vessels. As it turned out, these vessels were his own men. One of these men ended up cutting himself, resulting in an epidemic in Nelson Plaza. However, Team Arrow was able to contain the outbreak while those infected were cured by Palmer Technologies through Ray's nanotechnology.
Ra's then send a messenger to Oliver to tell him he would meet him so they could have a duel to finish this. Ra's met Oliver and mentioned how he would win either way. If Oliver would kill him he would become the Head of the Demon and if he would win his city would die. Ra's saw that Oliver used the sword he had been impaled with. Ra's and Oliver engaged each other in a sword fight. In spite of Oliver's considerable improvement from his training, Ra's kept the upper hand the entire fight and ended up taking Oliver down and destroying his sword in one strike. Ra's mentioned that thousands of men would mourn his death if he would die. He then attempted to strike down Oliver. Oliver disarmed him with the same move Ra's had used in their first battle and ended up impaling his chest, while refuting Ra's earlier claim, stating that his men would simply kneel before the next Ra's al Ghul. Oliver then recited the same prayer Ra's did after he had stabbed him. Proud of his student's success, Ra's handed him the ring before collapsing to the ground, dead.
After the death of Ra's al Ghul, things didn't go as planned. Rather than become Ra's al Ghul himself, Oliver passed down the mantle to Malcolm Merlyn.
Six months after Thea Queen went into the Lazarus Pit, she began developing a bloodlust. This resulted in her father urging her to kill people, due to the fact that Ra's al Ghul was already dead. Plus, even after six months, John Diggle still did not trust Oliver Queen. It took the combination of the death of Mina Fayad and the Green Arrow saving Diggle's life for them to finally make up.
Sara Lance's death still weighed heavily on Laurel, so when she learned about Thea's use of the Lazarus Pit, she traveled to Nanda Parbat to resurrect her sister. The attempt was successful, but the process resulted in both the loss of Sara's soul and the loss of Nyssa's friendship with Laurel. This would later lead to a civil war in the League of Assassins.
During Genesis, Oliver Queen mentioned the Outbreak in his speech to Star City.
Years later, Oliver Queen would call Ra's al Ghul an honorable man, despite the destruction the Outbreak caused.