I think we might need to wait until the 1st CBT to find out if the detailed storyline is actually related to Lithuanian mythology.
IMC Games mentioned that during the CBT we could get hold of the story by doing various quests so I'm really looking forward to check out.
But my guess is that since they have adopted the names of Lithuanian Pagan gods, I think the core storyline is actually based on it as well.
I guess we will all figure out it by this weekend haha
And the reason why they have adopted the seemingly rare mythologies from different parts of the world is that they wanted to avoid the general cliche formed in the gaming industry.
Flash has named a few up there, you know, Nordic gods (Odin, Thor, Freja, Frey, etc..) are heavily used in various games. Skyrim, is pretty much a Nordic. Valkyrie Profile (Japan-made) is also set in the Nordic mythological world.
For Greek mythology, oh we have so many of them. (Does Spartan ring you a bell?
If you look to the East, there is Hindu mythology. Vishnu, Rakshasa, and the Circle of Samsara... I would say Persona series are touched with notions of Hindu mythology.
Look at Japan. Japan is probably the most active country to game-ify / media-lize their own mythology. So many games and dramas and what-nots exist so I wouldn't even bother naming them.
So pretty much all of the 'major' mythologies have been in use already and maybe this is the reason they wanted some fresh change to the scene, hence Lithuanian!