A serpentine parasite who symbiotically lives inside the zombie Squigly. His presence prevents Squigly from becoming an undead servant of the Skullgirl.
Having been passed through the Contiello family for generations, Leviathan is refined and dotes on Squigly like her father, his previous host. This long familial history has made Squigly's bond with Leviathan deeper and more fundamental than that of most Parasites, and allows them to work harmoniously both in and out of battle like synchronized dance partners. Their unique circumstance also seems to have given them abilities beyond this world, as well.