The Citadel Council and the Systems Alliance fight for survival against the Reaper onslaught. However, the UNSC, politically divided and still recovering from the Didact's assault discovers a Mass Relay that will force them into the fight and change the course of galactic history forever. The Reclamation has already begun, and we are hopeless to stop it. ME3/post Halo 4

Earth has been decimated, its lands infested with hive, taken and fallen. The last remnant of the light grows brighter at the defeat of Oryx. A Baron rebels against his Kell and House to reclaim what his race once had, and an object in deep space is discovered by Dead Orbit. Discovering a new galaxy full of races that may help bring hope to all under the banner of the Traveler.

This is a tale of someone who doesn't know who or even what they are, but has a sense of wanting to travel the stars. (This is essentially my log of what I have discovered and in the character's POV)

It will not by just a stellaris crossover, there will be universes like warhammer, Beyond Earth and Starcraft