The Promorin are an ancient sapient species of plant-animal. Though they are not the first sapient species to achieve space travel they are thought to be the oldest having evolved around 10 billion years ago. Their homeworld is called Aptonus IV, a barren moon that orbits the gas giant Aptonus in the Cetus system.
Among the earliest civilizations in the galaxy, the Promorin made it their own goal to keep order among organic life. It would proceed to destroy species that would either become too powerful or too chaotic. Its methods were brutally effective in the past, but to this day, scholars debate on what caused their decline.
The Promorin appears as a collection of green-yellow fungus with several spore pods around its body. The creature is actually a large collection of microbial cells which act together as a massive super-organism. Much like a multicellular creature, the Promorin has several specialized cells which can create different objects, but are separate enough to actually be considered a collection of multiple species.
The Promorin has several large spherical pods that serve as capsules to process brain activity. It communicates by transmitting electromagnetic impulses to the target. In a sense, they are actually several giant brains, when put together have an astonishing processing power and intelligence, suggesting they were a formidable opponent in the past. Another notable feature is the cannon-shaped protrusions which are designed to fire sticky spores at objects.
The Promorin is native to a low-gravity planet with almost no atmosphere - it has survived entirely underground, feeding off of minerals. During the apex of its power, the Promorin would attack other species by launching spores into space that would attach themselves to spaceships. From there, it would spread from planet to planet.
What makes the Promorin deadly is that one colony alone was capable of destroying an entire planet's biosphere. Once a passing spaceship accidentally spreads the spore to a planet, it would proceed to begin absorbing the planet's microorganisms and any nutrients it can find, which effectively kills all of the planet's flora. With the lack of a life form to recycle oxygen into the air, other respirating life will soon die out.
The Promorin manages to pull this off in almost any environment by taking energy from geothermal heat, making it highly resistant even in extreme environments. To attack structures such as bio-domes, it will break off into microscopic "sabotage spores" which are capable of quickly growing into miniature Promorin to destroy machinery.
Likewise, it can also deploy toxic spores to kill off any other particularly versatile life forms. If they even withstand that, the Promorin can always result to simply engulfing the creature.
The Promorin's need to adapt to numerous different planets drove their evolution towards sapience.
Most Promorin tech comes from other early, ancient space travelers. They would steal spaceships by sending spores into the air, then overtaking it. As a result, the Promorin learned the technologies behind FTL travel.