The Nature of the creators was war. It is said the first conflict began moments after the creation of the this universe. All that was left of the old universe were its bastard children, birthed from the war at the end of all things. They came to this virgin universe and brought their war with them. They sought to establish a new world with the knowledge gained from the old one, but they brought their grudges and divisions with them. They built empires to sustain their war engines. At the height of the war it was almost like a golden age. But an eon of war took its toll. One by one, the great bastard empires fell, their knowledge lost, their great works broken.
The Bastards remade the galaxy in their image, then they died out. What was left was a weird teeming corpse of abandoned mega structures and autonomous weapons. Overtime, successor empires arose, prospered, declined and fell, and a new crop of empires took their place. By most reckonings we are in the third crop of empires, though there are decaying empires left from the second crop, and some newborns of the fourth crop. War is a constant threat, though the specter of mutually assured destruction ironically brings peace to the galaxy. All major powers know that if they upset the balance all they built could easily be destroyed. Instead there is an unending cold war of soft power and colonialism, as the empires annex solitary planets and spread their power and influence. The threat of cooperation is another potent weapon in the arsenal of peace, as if one power grows too strong or becomes too aggressive, other powers will form coalitions to take them down. The Galactic council is an ancient (post floozy) institution meant to give the galaxy a place to come together for peace. It is a hidebound and often ineffectual organization, crippled by a thousand different special interests, but it is also a useful trade hub and it gives spies a place to hang out.
After the bastard wars and the crops of successor empires, there are few planets untouched by civilization. Of all terrestial planets in the galaxy, it is estimated that around 60% of them have a carbon based biosphere, and some 30% have a machine ecology. The remaining 10% are some combination of silicon based life, exotic bioforms and truly barren planets. The majority of planets show some sign of colonization or contact. It is estimated that around 30% of worlds have some civilization currently living on them, either the remnants of a galactic empire or a naturally evolved race. As these newborns societies emerge, they enter into an unwitting race against time, to see if they can reach of level of sophistication where it is no longer profitable for an empire to annex them. Also of note are the many "freeholds" across the galaxy. These settlements are outposts free or mostly free from the control of a galactic empire, usually because they're not worth the trouble. These refueling stations, mining colonies and monasteries are the fringes of galactic society, home to pirates, freebooters and other assorted scoundrels. Some of these outlaw waypoints have existed for millions of years outside the attention of the galactic empires. Others prove too troublesome and are stamped out.
One of the galaxies most populous races is human kind. Human majority worlds make up an astounding 10% of settled planets, with human enclaves being common on many other worlds. The exact history of the human race is unclear. Some think they were one of the earliest successor empires, that they thrived in the vacuum left by the bastards before their empire collapsed. Others think that humans must have been a servitor race, spread through the galaxy to serve their bastard masters. Still others think that humans were bastards, at least one form they chose to take, though this theory is only really popular with human supremacists. There hasn't been a real human empire for thousands of years, the disconnected human worlds were isolated and easy prey for other empires. In the last hundred years, the seeder collective has emerged from the human home world of Dirt and has begun to reconnect the scattered bulk of humanity. The seeder collective is a young empire, brash and bold and looking to make its mark on galactic history.
The biggest barrier to intergalactic trade is space itself. The cost of transportation makes it prohibitively expensive to transport goods from system to system. Exotic elements and precision crafted machines are worth it, as are floozy artifacts and other oddities. Luxury food and drinks are popular with arstitos and worth importing. If bulk food can be produced cheap enough, its profitable in famine stricken or improvised areas. Drugs and other intoxicants are also popular exports.
In a galaxy as crowded and diverse as this one there are many religions, but only a few have spread beyond their home planet. One of the most popular is bastard worship, a form of scientism that holds up the Bastards as worthy of study and emulation. It is especially popular among races and polities that claim to be direct descendants of the Bastards, such as the Neo Floozy Empire. Kaiju worship is another common religion. It holds that virtue is a function of mass and that the largest organisms should rule over the lesser one. The people of the Whorl follow a specialized version of this. It is common on planets in the Republic of Sea serpents, though the sea serpents themselves generally don't buy their own hype. There are many beings in the galaxy who identify as gods. Naturally, self professed deities don't socialize with each other very well, but the psychic tumor Molsheen has by shear force of personality corralled a number of the more tractable deities into a loose pantheon. The Manifest Gods, as they are known, are a constant thorn in the side of the established empires, as they work together to spread their self aggrandizing creeds wherever they can. In more the material societies, believing in a god that actually exists in the universe is seen as an error in judgement.