The Leviathans were a race of beings who ruled the Earth before mankind came into existence. Their true forms were hideous and inhuman, although many Leviathans took human shape after they lost control of the planet. They longed to return to the Earth and reclaim it as their own (915). To that end, they seized control of the mind of Barnabas Collins in 1796 because he had mastered the power to travel through time and could carry the essence of their leader into the 20th century (886, 887, 938).
Paul Stoddard made a pact with the Leviathans, receiving wealth in return for his most valuable possession, to be collected years later. Realizing this meant his daughter Carolyn, he sought to break the agreement (900).
In their efforts to take over the Collins family and ensure the marriage of Carolyn Stoddard to one of their own, they had Barnabas use the Naga Box, a wooden box with the power to enthrall humans into the Leviathan cult. This mystical device did not always work however, due to resistant genetic structure in some people. Julia Hoffman was one of those unaffected (916), as was Maggie Evans (943).
The Leviathans were defeated when Jeb Hawkes, allied with Barnabas, destroyed the Naga Box during the ceremony to transform Carolyn Stoddard (whom he had fallen in love with) into a Leviathan. The Leviathan Altar and Jeb's true Leviathan form were destroyed by their actions. All members of the cult that had been enthralled during the recent events were subsequently released from Leviathan control with no memory of their participation in the group's activities (965, 966).
After 1970, Carolyn Stoddard thwarted an attempt by Doctor Gretchen Warwick to revive the Leviathans (Curse of the Pharaoh). Gretchen discovered an ancient Egyptian golden Naga Box and resumed the form of a Leviathan, like Jeb had, and killed the successful lawyer Frank Garner. Carolyn ultimately defeated Gretchen and the Leviathans by tampering with a spell through her late husband's assistance. In a parallel time band, Carolyn did not succeed in stopping Gretchen and the Leviathans, who laid the Earth to waste (The Flip Side). It's implied that in this time band that Carolyn chose to help the Leviathans, who rewarded her by making her a "Leviathan Queen".
In 1973, Quentin Collins thwarted an attempt to resurrect the Leviathans when he returned the Crimson Pearl to the sea before the Pearl had absorbed enough energy to bring the Leviathans back into existence (The Crimson Pearl).
- Leviathans and members of the Leviathan cult included Oberon, Haza, Adlar, Barnabas Collins, David Collins, Jeb Hawkes, Amy Jennings, Sky Rumson, Elizabeth Collins Stoddard, Bruno, Nelle Gunston, Megan Todd, and Philip Todd.
- The Leviathans were based on the literary works of author H.P. Lovecraft.