Qax

The Qax were an alien species from Stephen Baxter's Xeelee Sequence. They were lifeforms composed of convection cells, needing to live in turbulent substances. They subjugated humanity in the 51st century, farming the Earth for organic compounds and destroying human ships with their organic Spline Warships. The species was greatly weakened and traumatized when a human pilot forced the Qax to destroy their own sun with gravitation-wave "starbreaker" beams.

Biology
The Qax were massive beings composed of thousands of hexagonal convection cells. They needed to live in turbulent fluids to survive, such as water (like on the planet-girdling swamp of their homeworld), star matter and even spacetime. However, their bodies were extremely fragile and could be disrupted with ease. Their population was tiny compared to the teeming masses of humanity, due to the Qax not having much room in their ocean.

Technology
The Qax were capable of using their cells as molecular factories, for producing microscale technology. This could be sold on the galactic market for quite a profit, and the Qax were able to build a trade empire spanning light years. They flew around in Spline Warships, which were a sapient species on their own, armed with formidable technologies. These included singularities for a gravity field (how the Qax obtained these is unknown), pirated Xeelee weaponry such as the aforementioned starbreakers and a hyperdrive. However, the Qax were either unwilling or unable to produce exotic matter.

History
It is likely that the Qax gained a foothold in the universe long before humanity. They started out as a race that endlessly traded biomechanical trinkets among themselves, until they were discovered by a crashed alien spaceship. They were given ships by other races in return for the organic compounds they made, which were quite valuable. They also discovered and gained a limited understanding of the Xeelee and their projects, such as the universe's escape hatch, Bolder's Ring. The Qax also discovered and recruited the Spline as secure transport.

In the year 5088, the human race was brought under the thrall of the Qax, and had all of their AntiSenescence technology taken away, leaving the species to die like insects. A Governer was appointed, and affairs were mostly peaceful for almost two centuries. However, a GUT (Grand Unified Theory) ship called the Cauchy had arrived back in Sol with a wormhole (an "Interface Portal") capable of going back to the pre-Occupation Sol System of 3717. The Qax Governer was making preparations to observe the future outcome of this event when a purloined Xeelee nightfighter began attacking, killing the Governer. The nightfighter was under the control of a Qax, from the time after Jim Bolder forced the Qax to destroy their own star with starbreakers. This rebel Qax attempted go back centuries and rectify the timeline by destroying the Earth. However, this Qax's plan was foiled by Michael Poole, Jasoft Parz and the rebellious order called the Friends of Wigner.

The Qax Occupation was overthrown in 5407, and humanity recruited their Spline and took most of their technology. The last heard of the Qax was five million years in the future, when they fought off the Photino Birds with a red giant star flagship, allowing the Xeelee, humanity, Spline and Silver Ghosts to escape into Bolder's Ring.