The Sentinels are a highly-advanced synthetic-organic race . The Sentinels reside in deep space, the vast, mostly starless space between galaxies. They hibernate there, dormant for ages at a time, before returning to the galaxy.
These Sentinels are ancient; their true name Lunias(Idk). "Sentinel" was a name bestowed. In the end, the Sentinels spare little concern for whatever labels other races choose to call them, and merely claim that they have neither beginning nor end.
The Sentinels are the original creators of void-based technology, harnassing its power to uphold the mantle of power they have held over the galaxy. The Sentinels exist so that any intelligent life in the galaxy would eventually discover them and base their technology upon them – all part of a scheme to harvest the galaxy’s sentient life in a repeating cycle of purges that has continued relentlessly over countless millennia.
14 billion years ago, long before life even existed, the ancient stars that once populated the universe would experience the greatest event ever created, the Big Bang. The explosion lead to the creation of the Universe and with it, the subsequent galaxies, stars and even planets. Within one billion of it's creation the world was in chaos, stars crashed into stars, planets were destroyed by black holes or smashed into other planets, life was not possible at this time.
Four billions years have passed and the Universe has calmed down for the most part, things were beginning to cool down and slowly getting stable though planets and stars continued to collide with one another endlessly. But on a planet far away, near the edge of the known universe, an organic race was beginning to appear, but these lifeforms were far different. For whatever reason, this planet had high concentrations of Iron, Nickel, any heavy metals, Oxygen and even water, though it was in solid form. The life form that first formed came to be when the single cell organism that broke down iron, nickel, plutonium began integrating the minerals within their bodies and slowly over the course of nearly half a billion years, they grew and grew until the very first species to have ever existed began looking at the stars. They were tall nearly seven feet tall but these were their predecessors, they were tall, skinny and prone to 'rusting' or as they would call it, Metallic Decay. But they would serve as the ancestors that would give rise to the Lunaries. The ancestors were known as the Precursors, for they set in motion all life across the galaxy and as their time was passing, the Lunaries were given the mantle to begin their watch and protect life throughout the galaxy.
But at some point, the Lunaries adopted the name Sentinels during a forgettable age and soon adjusted their cause to exterminate the galaxy of life to maintain the counter balance, turning their intelligence towards mass weapons of war and technology that could change the shape of reality. Gravity-Based Weaponry was a favorite among them.