(YIL MAIN-jess)
These primordial beings inhabited the galactic core until the end of the First Galactic War.
Humanity’s initial encounters with them were fleeting. As we pushed further into the core, the Yims retreated further into the core.
Eventually a few minor skirmishes occurred, which were human forces testing the Yim response. The response was swift and total. Entire human fleets were wiped out before they could withdraw.
Humanity was prideful and began an offensive against the Yims. The particulars of the campaign are lost to history. But it is known that over the course of a few centuries, all of humanity was utilized for the war effort.
At some point, a plan was enacted that caused the war to end. The Yill Maingess were not defeated, but left the Milky Way Galaxy. Exactly what happened is also unknown at this time.
Very little is known about the nature of the Yill Maingess. What they look like and their biology was never documented.
The machines we faced in the war were a combination of massive spacecraft and enormous tripod machines that would assault planets.
The spacecraft would envelop an area of space kilometers across with tendrils of an unknown material. They would cause molecules within that space to break down into their constituent atoms.
The tripod machines would flood the area around them with energy that radiated out from them across the electromagnetic spectrum. This made them blindingly bright in all visual spectrums, as well as radiating tremendous heat and higher frequency radiation.
There were some successes against the machines on the ground. But later in the war, the Yims would atomize entire planets and star systems with their fleets.
Only the constant flow of resources from all of human space kept throwing enough matter at the Yims to destroy, they we reached a stalemate.
A portion of the plan to end the war involved using weapons that would have destroyed most of the stars in the inner core, where the Yim civilization was concentrated. However, those weapons were detonated prematurely by the Yims, wiping out a swath of human systems instead.
Shortly thereafter, they retreated from the galaxy.