Let's come up with a rich and complex alien world setting suitable for stories, pseudo-documentaries, or roleplaying games such as DnD. This can be an involved process, so I'd like you to just cover the basics first. We can refine the details further later.

I'd like a planet with a variety of biomes, inhabited by many creatures, much like Earth, but life on this world took its own path, with different plants and animals (and perhaps a different distinction than "plant" vs. "animal" to begin with)

There should be at least one sentient species represented in a wide variety of cultures and societies. They should have complex interactions with each other, and other species on the planet, and resulting from that, their own needs and wants and fears which ought to be relatable in context but may at the same time be strange, unusual, and, well, alien to humans.

But let's start at the beginning: Can you give a few broad, interesting biomes and how they might exist in their "wild" (pre-sentient) forms vs. how a local sentient species might have altered them over the ages?
While doing so, it is important to consider the solar system that planet is a part of, as other objects of the system, especially ones that are very close or very massive, may have a significant effect on the planet and its biomes.
Planet Name: Xylothar

Xylothar is a diverse and unique planet located in the Zykor System, with three moons - Orda, Talis, and Vynar - orbiting around it. These moons have a profound effect on the planet's tides, climate, and geology, resulting in a variety of interesting and distinct biomes.

1. Bioluminescent Forests:
In the wild, these forests are a mesmerizing sight, with plants and fungi emitting a stunning range of colors throughout the day and night. The fauna has adapted to this environment, using bioluminescence for communication, camouflage, or attracting prey. The sentient species, known as the Luminari, have harnessed the bioluminescent properties of their environment, cultivating plants for illumination and art. They've also developed architectural techniques that blend seamlessly into the forest, with buildings made from living trees and vines.

2. Liquid Crystal Lakes:
These vast lakes are filled with a liquid-crystal substance that supports a variety of aquatic life forms, some of which have evolved to have crystalline exoskeletons. In their natural state, these lakes are beautiful and serene, reflecting a dazzling array of colors in the sunlight. The Luminari have learned to extract and refine the liquid crystals for various uses, such as energy storage, building materials, and artistic expression. They've also constructed unique floating settlements atop the lakes, with delicate crystal structures that rise above the water.

3. Floating Sky Islands:
High above the surface of Xylothar, levitating landmasses form a stunning aerial landscape. These sky islands are home to unique flora and fauna that have adapted to the high altitude and low gravity. In the wild, these islands are a harsh and dangerous environment, with powerful wind currents and limited resources. The Luminari, fascinated by the islands, have developed advanced airships and technology that enable them to settle and navigate these treacherous skies. They've established a network of interconnected sky cities, each with its own distinct culture and architectural style.

4. Subterranean Caverns:
Beneath the surface of Xylothar lies a vast network of interconnected caverns filled with bizarre geological formations and unique ecosystems. In their natural state, these caves are dark and mysterious, teeming with life that has evolved to exist without sunlight. The Luminari have explored and settled portions of the caverns, using advanced biotechnology to create sustainable underground cities. They've domesticated certain cave-dwelling creatures for labor and transportation and cultivated unique fungi and plants for food and medicine.

The Luminari are a sentient species with a rich history, diverse cultures, and complex societal structures. They have a deep spiritual connection to their environment and have developed advanced technology that allows them to live in harmony with the various biomes of Xylothar. Their interactions with other species on the planet are intricate, often involving symbiosis, mutualism, or coevolution, which has shaped their worldview and cultural practices.