Leviathan is a transformation in The Binding of Isaac, added in the Afterbirth DLC.
Obtained by acquiring any 3 items with the devil tag.
+2 Black Hearts.
Grants flight.
Can be obtained as a rare reward from Sanguine Bond.
This page shows information as of the latest Repentance release.
To see latest up-to date information about this transformation for the new Repentance+ (Online Co-op) DLC, check this page instead.