The Master Chief is found by the Atlantis Expedition, how did the Master Chief end up in the early 21st Century and in the Pegasus Galaxy?

Just as the Atlantis team think they have finally found a reprieve from the Wraith thanks to a fortuitous accident something hidden in deep space and from another world may bring more than one complication to the fight

The Four Great Races once watched over thousands of worlds… but only one species was destined to inherit their place. Now, as an ancestral enemy rises from the ashes and threatens all life as we know it, humans from two different universes must learn to overcome their differences and stand together to reclaim the Mantle of Responsibility. Set shortly after the events of Spartan Ops

With the Covenant war over the UNSC can finally begin exploring the universe, but there first step outside their galaxy could lead them to another enemy that would prefer to feed on them instead of destroying them, can one ship survive in a galaxy teaming with an overwhelming enemy or will they get help from a group of humans who are also exploring the universe themselves.

The damage done to the Dawn during the slipspace jump had unintended consequences.

With the Covenant war over, the UEG has turned towards exploration and colonization again. The Pegasus Initiative was launched to start humanity's first ever out of galaxy colony. What the colonists find there however, is nothing they could ever imagine.

After the Pillar of Autumn escaped leading onto the event that would change the war. the Spartan who made it all possible survived the hell he was left in and has to work with a patchwork Spartan Team in order to survive and get back to Earth. (if something doesn't match the lore, don't yap on, all the answers are in the story)

On the way back to Atlantis, the USS Daedalus stumbles upon a wrecked Frigate floating in the void of space between the Pegasus Galaxy and the Milky Way. Will a weary expedition find unexpected salvation? Or will they add to the monument of Ancient sins?

"Never before had we encountered a race with powers that rivaled our own. Never did we imagine that the sins our past would come to haunt us again. In our overconfidence, we were unprepared and outnumbered." - Melia

The Ancients once ruled the Milky Way until they created the instruments of their downfall: Mankind and the Forerunners. They revolted and claimed the galaxy. Now their Revenge is ravaging their killers, and the children will soon meet their creators.

The war is over, but the Spartans don't know that. Desperate to find a way back into the fight, they inadvertantly stumble across ancient devices, and an alliance so old that no one remembered it ever existed.

A one-off that came from another idea I've been toying with. The UNSC get an unexpected visitor during the first Battle of Earth.