War Of Thirteen Billion Stars
A war 2 million years in the past. A war between galactic powers, a truly apocalyptic war. Resulted in massive desolation and destruction, and in the precursors retreating to their cluster.
A large empire threatened the others, and eventually the war began between the various powers.
Gigantic fleets were mobilised, entire planets turned to weapons, the stars used as gigantic beam weapons. Apocalyptic weapons and technologies were developed and used, based on some strange quirk of the universe's laws. Entire star systems were destroyed to keep the enemy from advancing, and fleet battles usually ended in death for any nearby planets and settlements.
The very galaxy.
Galactic devastation, the destruction of two species, and the retreat of the precursors to the cluster.
The abandonment of the galaxy overall, and a general uninvolment from all involved. Ruins of megastructures and constructs still dot the galaxy today, though not yet discovered by humans.
12 million years ago
2 million years ago
Pyrrhic victory for the Precursors and their allies.