Enceladus was discovered by William Herschel on August 28, 1789, during the first use of his new telescope. Alongside Jupiter's moon, Europa, Enceladus was considered a candidate for extraterrestrial life although Europa took more of the spotlight.
Endeladus formed over four billion years ago from the primordial planetary disc surrounding Sol. It was captured by the ever growing Saturn and became one of its major moons. In its early history, Enceladus' surface was liquid but with the cooling of the entire Sol System an upper layer of ice soon formed to cover the inner ocean.
Approximately 3.1 billion years ago, the first primordial life formed in the Enceladian oceans near the rocky floor near the hydrothermal vents. As with Europa, there were no exterior sources of extinction level events thanks in part to the protective ice surface layer.
Humans first landed on Enceladus during the Great Solar System Tour where they discovered the first evidence of life beneath the icy surface, but it wouldn't be until 2162 during the Project Deepdive mission when the Enceladus Subsurface Ocean Explorer or ESOE for short, came across small eel-like creatures living in the subglacial ocean.
Eventually more and more research stations were set up on Enceladus in order to study the natural evolution of a subglacial species. Terraforming the world was suggested and quickly abandoned as it was discovered that any major change to the undersea environment would do irreparable damage to the native undersea ecosystem.
By the year 172541, the native inhabitants had become as sapient as primitive homo sapiens and first contact was made between humans and Cheli in 172946. Since then, Enceladus has become one of the best scientific examples of actual recorded evolution of undersea intelligence.
Much like Europa, Enceladus has a thin upper ice layer crust which covers a thicker deep lunar wide ocean which itself sits on a rocky seafloor.
Large plumes and cryovolcanoes shooting geyser-like jets of ice particles from the heavily cratered surface into space, can be found around this frigid ball of ice. The oceans consist of hydrothermal vents and sometimes tremors caused by the tectonic activity.
There is a danger that Enceladus might be destroyed by the tidal force of Saturn in 30 million years. Fortunately, other moons of Saturn, such as Tethys, Dione or Rhea can also host the life of the moon.
The most intelligent and dominant lifeforms on Enceladus have been called the Cheli due to their resemblance to terrestrial eels. When they were first discovered, they showed slight signs of sapience and are the most intelligent species on their world. However, as humanity spread across the galaxy, the Cheli were showing signs of increased sapience, being able to craft primitive tools with ice shards from the upper layers and from the rocks on the surface below using their prehensile tails. Thanks in part to the abundance of Sealights, Cheli are actually capable of detecting visible as well as thermal light. The Cheli eventually reached primitive human levels of sapience around the year 172541 CE and first contact was made between humans and Cheli in 172646 CE.
Silent Creepers: Predatory shark-like animals that mainly pray on Cheli. They are very stealthy, being able to hide in the dark environment and will ambush any unlucky Eeloid or other small creature that swims too close.
Tripods: Organisms similar to starfish but with three limbs instead of five. They are considered to be the Enceladus equivalent of Echinoderms.
Sealights: Small bioluminescent plants that can be found in clusters, causing a beautiful light display. They emit a light blue color in their infancy and glow white in maturity.