Enter the whispered legend of the community: .
is primarily a multiplayer online brawler, and there is no official "offline" mode supported by its developers
Until then, log into Papaya Play (or the current publisher). Create a locked room. Fill it with bots. Turn off the chat. And pretend the world isn't ending. That is the closest any of us will get to Lost Saga offline for the foreseeable future.
If you want to truly play Lost Saga alone with no internet? That day may never come.