Lord of the Undead in the Land of the Risen: Satoru Suzuki dies a century before the Traveler brought humanity from the brink. Centuries later, Ainz Ooal Gown rises from the man's old bones, the fusion of avatar and gamer brought to unlife by a Ghost.
Idea I had while looking at a similar but different challenge, Ainz is risen by a Ghost from Destiny, complete with his extreme power and apathy for the living. How will he interact with a world that is so different from both the ones he knew?
He goes galavanting around Earth, killing and collecting everything he sees while forming a terrifying reputation for him to be confused by when talking to people, before heading off Earth or discovering some meatbags to care about (perhaps a female child warlock wearing a mask).
He either arrives in the Warlord era, the pre-games city era, or the time of the first/early seasons second game. The former gives him far more factions of humans for him to interact with, while the second gives a potentially interesting point of view on the Death God that appeared from nowhere (that reaction would be hilarious).
Free Under Glowing Skies: When Ranger Jack O'Nell learned he would be part of a team sent to the Cheyenne Mountain Complex, he expected a mind numbingly boring couple of weeks, not to find a giant ring that one of the egg-heads claims can send people to other worlds.
The NCR finds the stargate in the Cheyenne Mountain Complex a year or two before the events of Fallout 4. They manage to get it working with the computers and equipment left behind (some of it using Goa'uld tech) alongside the help of the Followers of the Apocalypse (including one Danial Jackson).
Due to its location, the Colorado Republic (a very militant government formed by remnants of the US military that has been fighting off the Legon for years and is now looking into NCR memberships) has to be added into the program (including the Daughter of one of their major military leader, Samantha Carter, later down the line).
They manage to get the gate working and travel to Abedos, where the events of the movie take place the same except the events with Ra end rapidly and with his ship mostly intact as a troopers response to a hostile alien ship with a sunroof is to launch a mini nuke into the giant hole, killing Ra and leaving the ship for the taking.
The new Stargate Alliance (starting with the NCR Followers and the CR) continues going to Abados and finds the stargate addresses, beginning exploration almost a year before it happens in SG-1, until the events of Children of the Gods happen.
Things continue on until, near the end of season one and with the Ha'taks on their way, the Alliance allies with the Big Empty led by the Courier, which had already been interfering. This leads to the discovery of a damaged Al'Kesh the US found (bought from the British in exchange for oil who stole it from the Egyptians), which the US used the computer tech from for the gate and used knowledge learned from it to build the US plasma weaponry and force field tech.
The events of stargate continue on with the nuked out, technologically advanced Earth that has energy matter converters (Sierra Madre tech made at the Big Empty that the Courier revived) that's also trying to colonize new worlds due to Earth being shity and the NCR trying to get worlds to join it.
Of Unknown and Unwanted Realities: When the Colonials discovered these new humans, they were confused; why are they so advanced, why don't they worship the gods, and who are these Tau'ri they so revere.
Bit of a twist on the standard BSG-Stargate crossover, the Colonials do not make contact with the Tau'ri, but a different, space capable human civilization (unsure if it should be a new one or one from the show). The colonials have to interact with the new human group while trying to discover how they exist, and how they got their hands on such advanced tech (some of their homegrown tech plus Goa'uld goodies). The human civilization has to deal with their new neighbors and the political situation around them besides the colonials.
Views from both sides are shown and, while the Tau'ri are mentioned, they don't show up until far later, having taken over the caretaker position of the Asgard and having advanced significantly (post disclosure, maybe 2040 to 2080?).
Of course, when the colonials find out the truth about everything (Earth being the homeworld, their gods being fake, their sub par technology, ect) they go ape ship and the Tau'ri have to interfere after hostilities break out.
The colonials then have to deal with their new, relatively minor, place in the galaxy, while many groups (think the NID and Trust) try and change that, to little success and much political damage.
Garden in a Sea of Shadows: When the Replacators came, the Nox, for the first time in millenia, feared for the safety of their world. So they jumped it to another universe, one filled with races who think themselves old, but act little better than the young races they claim to shepherd.
The Nox move themselves to the Babylon 5 universe, specifically Epsilon Eridani, the same system as Babylon 5 herself, during the early seasons of the show. The B5 universe gets the fun of an Elder Race that is somehow more open and more isolationist than the Vorlons.
The Nox gets a seat at B5 for *mumble mumble* reasons mumble mumble* it would be fun to read *mumble mumble*.
Death of Innocents: The Rachni Wars: When we went to the stars, we came with hope and curiosity. We found many who joined us here, and we began to think that peace and prosperity would be the only future we'd ever know. Then they came, the swarm that resurrected the fear, and doute and hate though left in the past like a demon bringing the dead to rom the galaxy.
An ambitious idea that I'm definitely not ready to try, and perhaps I never will. An attempt to tell the story of the Rachni Wars, a conflict that spanned three centuries and of which little is known.
This time period and the one before it in Mass Effect history have always intrigued me; there is half a millenia between the time of the Rachni Wars and the founding of the Council, an extremely long time by most standards. This proto Council era is almost a complete unknown, I don't think there are any colonies in the home cluster of the Asari made in that time (very odd). It would be very interesting to see what this age of peace did to the races active in that time, there had been no wars of such magnitude as the Rachni Wars or Krogan Rebellions, not even of the Morning Wars level as far as we know.
I lack the capabilities to tell this story to any satisfactory level, but I put it here hoping, someday, a person with those capabilities will see the idea, and be intrigued.
New Thrones and Virgin Stars: It has only been a few centuries since the founding of the Citadel Council, a short time for the Asari. On the frontier of known space, a new species appears, one wishing to claim its dominion across the stars as the first empires only begin to take shape.
Humanity makes contact with the Council only 300 to 450 years after its founding (200 to 50 years before the Rachni Wars) when the galaxy is young and it is a competitor in the great race, instead of millenia behind. Humanity competes with the races of the time, maybe with a few major wars, until the Rachni Wars begin (though less challenging as an opposing major power to the Council leads to more militarism and military developments). Then history goes on with mankind as a race longer on the Council than the Turians (maybe make them take the Alliance's place, that would be fun).
I like the concept but I have no idea how to make the story progress (like with Lords of the Traverse).
Weary Travelers Come with Fire: The Shanxi Expedition left human space hoping to build a new home away from the battlefield, they did not know that their final stop would bring them the Terminus, or that the battle had just begun.
In a late year of the 3rd millennium (haven't decided a date) a large expedition of people centered around a massive (for the Citadel Races) Arc Ship to travel deep into unknown space to get away from humanity. They end up deep in there Terminus after using a Relay to go farther. They are discovered after a few years (5 to 60) and get the joys of joining the galactic community, where half the people want to kill you, and the other half don't care (exaggeration, but you get the point).
The system the Expedition chose to settle holds a Secondary Relay that connects to Clusters 1700 light years away from each other, which each connect to several other notable Clusters. This gives the colony great importance and many problems due to many people, some of them undesirable, wanting to use the Relay, leading to a serious increase in their military forces and attempts to gain allies.
Human tech is more advanced in some ways, like cybernetics, computers, genetic engineering and materials science (also having cured aging for humans), while they are behind in other areas, energy production, propulsions, and some weapons.