Along with the a huge slew of art, info on the game's premise has also been apparently leaked, and while I generally don't like spoilers the premise for the game sounds incredible if pulled off correctly;
"Our story begins seven hundred years from now in the Last City on Earth, in a Solar System littered with the ruins of man's Golden Age. A massive, mysterious alien ship hangs overhead like a second Moon. No one knows where it came from or what it’s here for, but only that it’s our protector. Meanwhile, strange, alien monsters creep in from the edge of the universe, determined to take Earth and the Last City. We are young 'knights' tasked with defending the remains of humanity, discovering the source of these monsters and -- eventually -- overcoming it."
Hit the jump for more of the concept art and head over to IGN for the full story.