Leviathan was an organization headed by former Demon Head Talia al Ghul. It was used to combat against the Batman Incorporated army of Bruce Wayne. Taking the idea of the Oroboro, the main goal of Leviathan was to create a ring of terror around the globe which it would control. The Oroborus was meant to be immortal and indestructible, a quality Talia saw in Leviathan.
Leviathan started out as an idea by Otto Netz, a force that could oppose Spyral. Netz envisioned Leviathan as anti-capitalist, anti-god, anti-freedom and anti-man. He believed the organization would carry out mass murder, genocide, create child soldiers and harvest girls to fight for them. He believed it would change accordingly to the changes that would occur in Spyral.
After Netz was revealed to be working for both Leviathan and Spyral, a group of British superheroes imprisoned him on an island in the Falklands. Despite this, Netz maintained that Leviathan's Oroboro could not not be stopped. Following this imprisonment, Leviathan went dormant.
Talia al Ghul later took over Leviathan and used her resources to create the Heretic. On a day that Netz predicted the snow accurately, Leviathan rescued him from his island prison, allowing him to leave a dummy there to pose as him. To showcase Talia's power, Netz suggested her imagery be a mix of warlike colors and represent female archetypes of Kali Ma, Medusa and Tiamat. Instantly starting with child soldiers, Leviathan challenged the budding Batman Incorporated and declared their return. Agengs El Sombrero and Scorpiana fought Batman and El Gaucho in Argentina. Johnny Valentine was then pursued by Batwoman, but he escaped from her. Leviathan suffered its first blow on Netz's former island prison as Scorpiana was defeated by Batwoman. Due to Talia's aquisition of the nation of Mtamba, Leviathan was able to start creating its army of child soldiers there. This activity was discovered by Batwing. Under Talia's rule, Leviathan ended up having literally ten thousand eyes, fists, faces and weapons. The first five hundred soldiers of Leviathan were given the objective to infiltrate and contaminate others to Talia's ideology. Of these five hundred, the youngest was eighteen months old. They also began to send out mind control agents through simple products like chewing gum. Leviathan first began to target agents of Batman Incorporated by going after Man-of-Bats and Red Raven. Corrupting Miss Hexely of St. Hadrian's Finishing School, Leviathan succesfully infiltrated Spyral and got the Deputy Headmistress to sell out the students. However, both Hexely and Johnny Valentine were stopped by Batman. Otto Netz was then attacked directly by the Batman Family in the Labyrinth of Doctor Dedalus. In the attack, Netz was murdered by Robin. Placing a bounty on the head of Robin, Talia revealed herself to Batman and challenged her beloved.
Wherever crime, poverty and inequality flourished, so did Leviathan. Arriving in Gotham City, agents of Leviathan began to set up Lone Star Brand butcher shops and were identified by the grotesqueries they performed and their goat masks. The goat masks were made to mock Gotham's original meaning as "Home of Goats". Every thursday, to honour Kali, Levaithan would sacrifice a scapegoat at the House of Assassins run by Merlyn. One by one, prominent citizenry of Gotham were simply replaced. Of impoverished neighborhoods, school teachers began to teach the children the ways of Leviathan. The knowledge sunk in easily as the children were from homes of neglect. Men of Leviathan began to infiltrate the GCPD and the Gotham judicial systems. The plan was to ensure that there would be less and less of Gotham, and more and more of Leviathan. Talia met with the mobsters of Gotham and commanded them to eat what Leviathan ate, drink what Leviathan drank, embrace Leviathan and consider themselves lucky. When two mobsters known as the Brothers Grimm protested, Talia tricked one of them into eating the other which led to all other mobsters declaring loyalty. Leviathan then got the Mutant Gang into working for them on the streets. Answering the summons of the League of Assassins, Talia headed off to meet with Ra's al Ghul and usurped the League for herself. The House of Assassins was then attacked by Batman Incorporated and neutralized. Despite this, Leviathan quickly rebounded and through an attack on a compound on Park Row, managed to incapacitate Halo, Looker, Freight Train and kill the Knight.
The Heretic easily defeated Batman, allowing Talia to temporarily remove him from the equation. Talia also realized the dream of Otto Netz by finally creating the Oroboro Meta-Bomb. Nightwing and Robin were overpowered and defeated by the Heretic in a battle that left Robin dead. When Batman arrived, he and Nightwing managed to push the Heretic back and retreat. As a result of the chaos caused by the Battle of Gotham City, Leviathan managed to cause Batman Incorporated to be illegalized. An enraged Batman defeated all of Leviathan's Man-Bat assassins and brutalized the Heretic, whose failure to defeat Batman resulted in a swift execution via Talia. Batman Incorporated agents fought soldiers of Leviathan around the world in victory in order to disable Batman and Talia fought one on one in a battle that ended with Wingman handing over a disabled Oroboro detonater. Leviathan was ended by Spyral after Luka Netz executed Talia al Ghul.
- El Sombrero - Recruited to act in Argentina.
- Scorpiania - Recruited to act in Argentina.
- Una Clairemont - Recruited on behalf of Scorpiana.
- Lord Death Man - Recruited to kill the Outsiders.
- Tommy Merlyn - Transferred from the League.
- Johnny Valentine - Helped infiltrate Spyral.
- Miss Hexely - Helped infiltrate Spyral.
- Lord Death Man - An immortal Japanese crime lord.
- Jack Ketch - Executed scapegoats for Kali.
- Anya Volkova - Joined the fight against secret societies.
Dr. Dedalus originally envisioned Leviathan as the opposite of Spyral. He saw it as a terrorist cabal that would organize mass murder and genocide, create child soldiers and turn girls into weapons. The plan, though, was for Leviathan to continually change what it was and adapt.