( I do NOT own Mass Effect. Dead Space. Halo. Destiny or XCOM they each belong to their respective owners.)
(A/N: There will be changes to the Mass Effect timeline and Humanity especially.
One big change is ES/GS in this new timeline before First Contact, Humanity is 200 years ahead of the Galactic Standard Year. after joining The Citadel Humanity will mostly convert to the GSY.)
[ ES - Earth Standard ]
•
[ GS - Galactic Standard ]
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Prehistoric Times - The Precursors reach the Milky Way seeding it with life and later retreat to observe it's evolution from the safety of Path Kethona, many years later one species The Leviathans evolve quickly and dominate the Milky Way, enthralling every new sapient race they encounter and protecting them in return for tribute. With no knowledge of the Precursors existence the Leviathans consider themselves the galaxy's first and only apex race.
The First Harvest - After observing that their subservient races create synthetic races who consistently and violently rebel, the Leviathans create an Intelligence to seek a way to permanently preserve organic life. The Intelligence constructs an army of "pawns" to gather genetic information throughout the galaxy. Several years later the Intelligence betrays the Leviathans, using its pawns to slaughter them for their genetic material to create Harbinger, the first Reaper.
Unknown BCE - Several cycles after the First Harvest, the Intelligence builds the mass relay network to increase the efficiency of the cycles, allowing galactic civilizations to develop faster and more consistently between harvests. Using a recently indoctrinated insectoid race that will come to be known as the Keepers to maintain the Citadel, the heart of the relay network.
c. 2,000,000,000 BCE - Several Black Markers enter the Milky Way from the direction of the Triangulum galaxy.
c. 1,000,000,000 BCE - The Leviathan of Dis, a Reaper, is killed by the Leviathans. Its corpse comes to rest on the planet Jartar.
c. 65,000,000 BCE - The Black Marker, traveling through space, hits Earth and causes the mass extinction of the dinosaurs.
c. 37,000,000 BCE - An unknown spacefaring race fires a mass accelerator round at a Reaper near the planet Mnemosyne. The round penetrates the Reaper, disabling it, and continues moving through space, eventually striking the planet Klendagon and creating the geological feature there known as the Great Rift Valley.
c. 15,000,000 BCE - The Precursors seed the species that would come to be known as Forerunners on the planet Ghibalb.
c. 14,000,000 BCE - Humanity is seeded on Erde-Tyrene the ancient Earth, by the Precursors.
c. 10,100,000 BCE - The Precursors choose early humans to be the next species to carry the Mantle. Desiring to seize the Mantle for themselves, the early Forerunners rebel against the Precursors and wipe them out almost entirely.
After the Forerunners hunt down all of the Precursors in the Milky Way galaxy. The remains of the Precursors retreat to Path Kethona; the Forerunners' Warrior fleets pursue them and proceed to finish their work.
In the face of extinction, most of the Precursors reduce themselves to inert powder, intending to regenerate their forms later. However, one intact specimen remained in deep stasis and is buried within a remote asteroid a million years afterward.
c. 9,100,000 BCE - The Primordial, a dormant Precursor, arrives on the edges of the galaxy.
c. 2,000,000 BCE - The alien inhabitants of Tau Volantis discover a Black Marker, later building Red Markers across the planet's surface in the hopes of harboring more energy for their uses. The Black Marker triggers a Convergence Event creating a Brethren Moon.
The aliens construct a Machine flash freezing Tau Volantis and halting the Convergence Event. The aliens become extinct in the process.
