After getting down to the lithograph we are confronted by some enemies, but we never actually have to fight them as Leviathan kicks their arses back to the N-Zone. However you now have a choice: Fight the monster that has just appeared Leave to fight another day. Of course I chose to fight it. Leviathan was fairly easy for me to beat, but then again I did have Guardian so i cut the damage from tidal wave in half nearly. After beating Leviathan you now have a pretty strong summon to use. You can exit by jumping into the waterfall near the bottom of that area.