The Leviathan Path is one of the possible endings in Armored Core: Last Raven.
This path is a bit more AC intensive so don't do it unless you're confident or have already beaten one of the other path. There are numerous ACs being fought including Alliance's top two: Evangel and Jouster. The final boss of this secton is the Leviathan Trio but they're only collectively as strong as the Leviathan fought in Launch Preemptive Strike. It is also worth noting that it is fully possible to reach this ending without fighting or coming into contact with a single Pulverizer