Leviathan first appeared in Dark Reign: The List - Secret Warriors and was created by Jonathan Hickman and Stefano Caselli.

Little is known of this mysterious organization, save that it was born out of the Communist Bloc in the same way that Hydra was born out of the Axis powers, and that Leviathan brought 100,000 of the Eastern Bloc's finest Cold War agents to the facility known as Cold Storage, where the majority were placed in cryonic suspension until needed.

Apparently, the higher ups of Leviathan were involved in a collaborative game with the Hydra leader Baron Strucker, S.H.I.E.L.D.

leader Nick Fury, and Hand grandmaster Soji Soma where the meeting was set by Aries.

Hydra and the Hand struck back, stealing the alien power source making it so that the tanks would turn their occupants into monsters.

Nonetheless, Kraken informs everyone that the Psi-agents that had been retrieved from Red Worm have been repurposed to find the traitor.

[4] Madame Hydra presents the Japanese box to Leviathan leader Magadan, much to the dismay of Viper.

Madame Hydra then takes off her headdress to return to her identity as Valentina Allegra de Fontaine.

Magadan's lieutenants then hook up the box and defrost one of the containers awakening its occupant Orion.

"[5] Hydra arrives at Long Winter only to find it deserted except for a few squads left behind and the corpse of Viper.

When the device recognizes his voiceprint, Orion's message plays that despite the unfortunate mishaps between their two organizations during his sleep, they should meet at the Crown in three days.

[6] Ten days ago, the Leviathan delegation has arrived at the Hydra base called the Crown in Kyoto.

Orion, Magadan, and Valentina Allegra de Fontaine have arrived to meet with the leaders of Hydra.

Valentina is more shocked to see Viper alive with tentacles on her head and having regained her status as Madame Hydra.

[8] At the newest Leviathan base Perestroika, Orion and Valentina plot to assault Gorgon and Madame Hydra.