The Three Hundred year Stillness and the Dark War.

After the fall of the Rattaki Empire, there was an era of peace and commerce, but then the Dark Age settled in and hyperdrive technology was lost, and so the Three hundred year Stillness began.  The Three hundred year Stillness is another name for the dark age, nothing happened, there was no space travel, people forgot about other planets and other alien species.  After the three hundred years tuans and galxthoricans reinvented hyperdrive engines, so the Republic continued.

The Dark War started in 50023 BE, six hundred years after the Three hundred year Stillness.  The Republic had just discovered the carisyte species, who came from a Wild Space world, which they had destroyed, being a parasitic race.  And the race that called themselves "The Primordials" came to conquer the universe.  The primordials are a unique species, they can, at will, turn incorporeal, transparent, though they could not harm solid things in this form, lasers would pass right through them.  The carisytes and primordials combined made a great plague on the galaxy, the carisytes permanently damaged many planets and the primordials won every battle they fought.  That is, until the invention of the disrupter, a device that disintegrated solids, vaporized liquids, and dissipated gases.  When the primordials go incorporeal, they are technically a gas, so the disrupter dissipated them when they went into ethereal form.  The reason it is called the Dark War is because, even after the vaporizer, the war was long, and destructive.  Finally at the Battle of Nyx, the carisytes were driven back into wild space, and the primordials were banished from the galaxy.