Theia is a 7 billion year old moon of a gas giant orbiting an orange dwarf star thousands of light years away from the Sun. It has an atmosphere three times as dense as Earth's and very little liquid water left on its surface. Its oceans dried up millions of years ago but much still remains frozen in the form of ice. Every summer, this ice partially melts, creating huge flash floods across the surface. The native life has learnt to adapt to these extreme changes, much in the way life on Earth has adapted to the planet's seasons.
Complex vegetation on the planet is restricted to areas of geothermal activity which melts the ice providing the plants with enough water to survive. One of the moon's few species of tree, the 'Trumpet Tree' has roots that can reach hundreds of meters underground. Attached to its branches are trumpet-like funnels pointed upwards at the sky to collect as much precipitation as possible, which only falls during the summer. These geothermal hotspots are rich with biodiversity but are also very dangerous. Some plants, such as the 'Spear Plant', grows meter long projectiles that are thrown from the plant whenever something approaches it.
On the rest of the planet, plant cover is very sparse.However, underground, all the plants are connected in a mycelia-like network of roots to exchange information and nutrients. Only a simple grass-like cover can grow on the dry surface, where the only water available is in the planet's constant mist. A significant amount of the vegetation on Theia is predatory, and employ tactics such as bioluminescence to lure prey close. Canyons and riverways are densely populated with perennial plants that only grow when they sense water during the flash floods of the summer. All plants on Theia reproduce via spores.Some species of plants have taken advantage of Theia's low gravity and high atmospheric pressure. One such plant, the 'Balloon Plant', inflates a sac of air and rises to the cloud level to collect precious water and to spread its spores.
Like plants, all life on Theia reproduces via spores. This suggests that all of the animal species are descended from vegetation or fungi-like life that very early on lost the ability to photosynthesise and instead began to aerobically respire.
The low gravity and dense atmosphere allows animal life to grow far larger than on Earth. One animal lineage, nicknamed "The Leviathans", resemble mammals on Earth but are larger and typically have more limbs. These rare creatures are becoming extinct as Theia's now limited water supply cannot support them.
The dominant animal holotype on Theia is long necked, six limbed herbivorous grazer similar to the antelope on Earth. Most species on Theia see in infrared as they need to be able to detect geothermal hotspots from kilometers away.These animals typically roam Theia's salt flats, huge areas of land where the last oceans dried up, searching for a fresh water spring or river. While Theia's oceans may have dried up, there are still huge underground reservoirs of fresh water, kept thawed by volcanic activity.
The natural predator of larger prey such as the Leviathans are underground creatures. Many creatures avoid the surface due to its seasonal climate and lack of precipitation and instead have evolved to live and hunt underground. These animals typically resemble large burrowing insects, and have constructed huge underground colonies, some of which stretch for hundreds of kilometers and are used by a number of different species.
Life on Theia evolved underwater, and in the ice caps some marine life still remains. They resemble fish on Earth but without eyes and with a sonar organ instead like much of the surface and aerial life on Theia. When the ice thaws they have just two weeks to reproduce and prepare for hibernation. When winter comes, the fish produce antifreeze protein and go into a coma-like state until the summer arrives next year.
Some of the animals of Theia have taken to the skies, too. Many of them have involved inflatable bags of lighter than air gases that allow them to control altitude. The largest of these animals, the 'Air Whale', resembles a whale with insectoid legs similar to a flea's that allow it to propel itself off of the ground. Most of the animals are gliders simply there to harvest water from the low-altitude clouds, and travel in huge flocks. They are hunted upon by faster, more agile wasp-like creatures that have evolved powered flight and dominate the ecosystem.
There are no intelligent species on Theia. Even after seven billion years, evolution hasn't produced a sentient species. This is because human-like intelligence is a fluke, rare event that is not favoured by natural selection and therefore is very unusual in the galaxy. The most intelligent species on Theia is the 'Swarm wasp', a partially subground partially aerial hunter. Their overall intelligence is high but they share a hive mind and therefore each individual isn't truly intelligent.