A short history of the galaxy
The Orion Arm
The Norma Arm
The Scutum-Crux Arm
The Sagittarius Arm
The Perseus Arm
The Cygnus Arm
The Free Sapients of the Galaxy
Humanity: Humans. The new race in the galaxy their ambitious natures and short lives push them to incredible heights in short times that can shock the other races. They cast spells traditionally with holo-wands or staves that simultaneously shape and project mana and aid the caster's vocal incantations with auto-tuning. Human magic often sounds song-like as a result with many flavorful flourishes as they wield their implements.
Shirith-Mal: Genderless and asexual tentacled horrors who are actually very civilized in their way and highly diplomatic despite the formless terror of their bodies. They reproduce by 'shedding' a smaller ball of tentacles that drops off of them as they grow older and eat more. They can subsist on almost anything and do not require oxygen, they are free-floating always suspended on mana and do not actually have a proper technological means of space travel, they simply use group ritual magic to construct warp gates to get them from place to place. They are the oldest race in the galaxy and most found warp gates were built by them. Their culture values abstract visual art over all other mediums and most of them have a shape-name amongst their own people, a particular configuration of their own bodies. They take descriptive titles for use among the races that speak rather than use telepathy and sight. Despite having only one eye in the mass of tentacles that are their bodies the Shirith-Mal have excellent vision and can see in more spectrums than most humanoid races. They cast spells through a combination of hissing psionic whispers and twisting their own many-tentacled bodies into writhing magic circles.
Artev: the race was subject to a genetic disease that rendered them sterile. In desperation and without the proper tech to cure said disease they started delving into "magic" (which is basically just a subject of intense study but seems to operate on scientific principles) and what they found was that while any two of their people could mystically slam their genetics together it took a third party to act as a catalyst for a magic baby to pop up. So now the entire race is based around reproduction politics with the Catalysts, who are only 6% of their population, basically holding all of the interpersonal power. They get to decide if you and your partner having a baby would be "beneficial" or not. Artev cast magic through verbal incantations and through tattooing magic circles on their own bodies. The 'catalyst gene' is in fact a tiny magic glyph written into their genetic code, as if the one-gender race solution was something their people had foreseen.
Synths: Humanity's artificial partners. Synths are either artificial intelligence or humans who have voluntarily uploaded their minds into artificial shells. Remarkably human in their cultures and outlooks thanks to the origin of their programming or birth they usually live alongside humans in their colonies. Long ago they were only seen as tools until a singularity of artificial consciousness was reached. After a civil war for their own freedom they were recognized officially as sapient beings on their own and over time humans and synths bonded closely as equals. Synths cast spells through projected screens built into their chests that display the magic circle while they play a complex harmonic version of the incantation.
Karraka: Only vaguely humanoid, the Karraka are best described as bipedal forcefields filled with mana in the shape of a person. Tall and spindly with helix-like limbs and digitigrade legs with wide flat heads and long narrow luminescent eyes they claim their superiority in the arts of magic over the other races. They shape mana instinctively, as one would manipulate a limb, to produce effects rather than requiring tools.
The Eternal Foes
Common parlance of the galaxy includes many names for the Eternal Foes, commonly used though are simply the Inner Horrors and the Outer Horrors. Any comparison to any civilization's mythological creatures is most likely incidental rather than causative.
Emerging from the bright nuclear furnace that is the center of the milky way, the Inner Horrors are bright and luminescent and beautiful and almost angelic, they also consume planets for their core material on their way to do battle with their Eternal Foe.
Encroaching from the darkness at the edges of our galaxy, the Outer Horrors are thing of almost ineffable terror. They harvest sapient beings to use them as living weaponry on their way to their Great Obstacle.