Plot

The basic plot of Rain World is described in this article, describing the path a new player is most likely to take. Deeper lore exists within the game, but is much harder to find.

The Plot
You play as a, a nomadic, omnivorous creature who relies on a small herd community, intelligence, and the use of simple thrown tools to thrive in a world filled with predators and periodic torrential rains. As a deadly storm approaches, the Slugcat stumbles during a climb and is separated from their family. Left alone, they must struggle to survive, and eventually thrive, in a dangerous and unforgiving world.

Mysterious guide
Shortly after starting the game, the player encounters a who takes an interest in the Slugcat, acting as their guide for reasons unknown. The creature helps the Slugcat survive by pointing out food and shelter when needed, as well as alerting them to threats. As some time goes on, the creature begins guiding the player along a given path, showing symbols and pictures which indicate you are heading towards the Slugcat's lost family...

As the Slugcat's journey goes on, they encounter a variety of strange creatures, including other sentient life in the form of [s. The guide helps the Slugcat deal with these creatures. As the journey continues, the guide stops indicating the presence of the Slugcat's family, and begins urgently directing the Slugcat to a strange humanoid being...

Looks to the Moon
Far out in the [, the player eventually finds a vast mechanical complex in shambles, and the guide directs the Slugcat inside of it, indicating that the being within may be able to assist them. Within the complex, the player eventually finds a seemingly helpless blue robotic creature in a heavily damaged central chamber, which they may later discover is Looks to the Moon. However, she is unable to communicate with the player through anything more than incomprehensible chirping, and offers no apparent help. Several small circling Looks to the Moon may catch the player's eye, however, offering the player another course of action...

A New Friend
Should the player opt to ignore the Neuron Flies, the guide suddenly beckons the player upwards towards a new destination. The guide indicates the desire for the Slugcat to return with additional Neuron Flies for Looks to the Moon, who is suffering from a lack of processing power and memory. Such is Looks to the Moon's deterioration that she won't even remember the Slugcat's visit until something more eventful happens.

Stolen Enlightenment
If the player grabs hold of a Neuron Fly, Looks to the Moon panics and tries to get the Slugcat to drop it. Should the player eat a Neuron Fly, Looks to the Moon cries out in distress and writhes in agony, apparently seriously damaged by this. Slugcat begins to glow, however, gaining a trait referred to as 'enlightenment'. This helps the player get through certain areas of the game, but the guide takes the Slugcat's betrayal very seriously, reacting angrily and leaving the Slugcat by themselves. Curious orange spirits are the player's only guide upwards, towards a new unknown structure...

Five Pebbles
Journeying upwards leads the player to scale and eventually enter a sprawling compound filled with unusual threats. The structure appears similar to Looks to the Moon's, but in a much less damaged state. At the heart of this compound lies another Iterator,. Upon entering this chamber, Five Pebbles examines the player, briefly attempts to communicate, and then proceeds to insert a chip into the Slugcat's brain, granting the player the Mark of Communication. He infers the Slugcat wishes to escape the cycle of reincarnation they are stuck in, and directs them towards a spot deep in the earth, where they can free themselves from the cycle.

Returning to Moon and Stealing Neurons
With the Mark of Communication, the player is able to return to Looks to the Moon and communicate with her. Looks to the Moon has much to say, but is not very friendly if the Slugcat ate any of her Neurons. If the player follows the advice of their guide and steals Neurons from Five Pebbles to return to Looks to the Moon, she becomes thankful, maybe even forgiving the Slugcat if they had eaten a Neuron previously. Bringing Neurons restores some of Looks to the Moon's memories and abilities, and she is able to read s brought to her, giving the player much more insight into the history and lore of the world.

Ending
When the player reaches the Depths, they discover a temple guarded by. Thanks to either the Mark given by Five Pebbles or the blessings of the es, which bestow a higher potential for Karma, they let the Slugcat pass without trouble. Deep within the temple lies a lake of void fluid into which the player must dive. After diving for some time, a godlike being assists the Slugcat in ascending. Its old life gone, the Slugcat seems to reunite with the souls of many other Slugcats, perhaps including their family. It is important to note that some time after meeting the other Slugcats a white light appears, which the player must swim to in order to finish the game.