Several billion years ago, a nebulous cloud of gas and matter began to gravitationally collapse. For nearly a million years, a protostar gathered matter until the molecular cloud was depleted in all the areas closest to it. Eventually, it became a F1 star. As it started to head towards main sequence, the protoplanetary disc around it began to collapse even further.
Close to the star, two rocky planets formed. Farther away, two more planets were born - these ones, gas giants, unable to become stars in their own right thanks to the influence of the primary star. Only one planet truly matters, for it is the planet that will - many millions of years from its formation - eventually form life. There is no life yet, let alone any sentient life that could name this planet, so for now, we shall call it "Homeworld".
Homeworld once had a stable orbit around the star, bordering on truly circular. But a rogue planet crossing the galaxy and the solar system, three-quarters of the size of Homeworld, slammed into it early on in its formation. This rogue planet had water on it, and not only did Homeworld acquire water, so did its three moons.
The rogue planet gave way to many of the planet's unique features - a very heavy, iron-dense core and its large magnetosphere, the three-and-a-half moons (more on that "half moon" later), the water that makes it up, and its highly eccentric orbit.
What was once stable became erratic, the rogue planet having knocked Homeworld off course. While it spends around two-thirds of its time in the habitable zone of its star, at its aphelion entering the season of winter, in its heated summers it drifts closer and closer to the star it orbits, making the sun appear larger and the solar winds it is subjected to harsher. Yet because of its magnetosphere being so encompassing - even surrounding its moons - it manages to cling to its atmosphere. And the atmosphere itself is enough to protect its surface from being burned and stripped away.
So exists Homeworld: an unusual planet with just enough ingredients for life, nearly unbelievable amidst a universe of many other unique, incredible phenomena.
Though science seeks answers, there are many questions that remain. One of those most pressing, most interesting, questions is how life first formed. Was it seeded from some progenitor (and, if so, how did that progenitor first come to be)? Did it form with molecules interacting with each other, RNA eventually giving way to DNA? Is there some mysterious other force that built life, something else unknown, that fueled the existence of what is known as "life"?
Homeworld does not hold these answers. Simply: one day there wasn't life, and then there was. It began with extremophile prokaryote bacteria, existing and feeding off of deep sea vents. These extremophile prokaryotes lived and died rapidly, mutations, mergers, and separations happening at a speed much quicker than typical evolution on Earth, due to their simplicity, lack of organelles and singular, circular chromosome.
The first mutations pushed these primitive bacteria away from the vents, towards the surface of the ocean and towards the sun. And from there, the first cyanobacteria arose - allowing oxygen to enter Homeworld's atmosphere for the first time.
But cyanobacteria did not give way to plant life. No; other mutations within the first bacteria gave way to archaea, midway points between prokaryotes and eukaryotes. These archaea were also extremophiles, but they began to become more complex - multiple strands of DNA, sometimes primitive organelles, and other differences marked them as not quite eukaryotic but no longer prokaryotic.
It took nearly two billion years before familiar life formed. The first eukaryote cell was a type of protozoa, a unicellular microorganism with membrane-bound organelles and different types of locomotion such as flagella or pseudopodia. From this first protozoa - which shall be referred to as the Progenitor, the first eukaryote traceable on the tree of life, there gave rice to unicellular algae and fungi. In time, algae will become multicellular plants; fungi, too, will become multicellular; and the Progenitor will find new forms that evolve to more actively consume food. This is the beginning: plants, fungi, and animals, waiting to bloom into diverse and varied forms.
Homeworld has three moons, two of which are quite close to the planet. The nearest moon is very tiny, and the next-farthest moon is only slightly bigger. These moons appear to be roughly the same size in the night sky, although their orbits are quite different from each other so that they are rarely close together.
The third and largest moon is dubbed the Primary Moon because it is so much larger than the other two moons. It's much farther than them, but the size difference is so vast that it retains a large appearance from planetside. It even has the strongest effects on Homeworld's tides, simply because it is so big. It is even one and a half times the size of Earth's own Luna, which means that though it orbits further away from Homeworld than Luna does from Earth, it still has the appearance of its large size.
And then there is the half-moon. Visible from the planet only occasionally, remnant rocky - and icy - debris from the planet's long-ago collision that formed its moons hovers in the L1 lagrenge point between Primary Moon and Homeworld. When the sun hits just right, when all three proper moons are either hidden by clouds or new, the ominous Shadow Moon will appear. From Homeworld, it appears roughly circular, yet it clearly is misshapen. One day, eventually, the life on Homeworld will consider its appearance a bad omen.
But for now, life is not enough to consider anything at all, other than where its next meal may be.