Yep, exactly what it says on the... thread title. The Forerunners, after 300 years of war with the Flood decide "f**k this noise" and the jump the entire Maginot Sphere into a different universe. Unfortunately for all parties involved, they arrive in 40K(in some previously empty sector, if none a thousand lighyears across are available, their above the galactic plane). Due to their other-universe-y-ness they are distinctly lacking in a warp presence(there is sod all there). The Ark and the Halos are left behind, but there is nothing to stop them building more. How badly does the shit hit the fan? (Note: due to 300 years of hopeless war, these are the Forerunners after they become more willing to "bend" the rules sooner, and so are no longer as interested in their 'Mantle' but are instead far more interested in reasserting themselves(although no necessarily through war(althought this IS the most likely outcome, given this is 40K.)))
