The Sheep

An unnamed narrator is approached in Haruki Murakami's novel A Wild Sheep Chase with seeking out an enigmatic Sheep with a star on its back.

A Wild Sheep Chase
The narrator possesses an old photograph from his friend "The Rat" portraying a rather nondescript scene of mountains and sheep before them used for a life insurance advert. He is then drawn to the associates of the Boss, an enigmatic power figure behind the scenes and self-made man of a great society. The Boss' secretary points out an unusual sheep among the flock appearing in the image that possesses a star-shaped mark on its flank. Being of great interest to those working under the Boss (due to the Boss suffering from a blood cyst among other ailments and seeing the sheep in hallucinations), the secretary gives the narrator one month to find out the sheep's location or else. Deciding he has nothing to lose, the narrator goes on the mission with his girlfriend and tries to seek out The Rat for information.

As the plot goes on, the narrator and his girlfriend meet up with an unusual figure called The Sheep Professor. The Sheep Professor discusses his past where he developed a "spiritual communion" with a sheep that was allegedly residing in him. Said sheep resembles the one found in the photograph and is of a supernatural form. Previously, the Sheep had taken The Sheep Professor as a host after he had unintentionally disturbed its slumber in a cave and essentially used up the man until he proved useless to the Sheep's cause. Discarded, The Sheep Professor is left a still-alive but worn-out, shut-in, and obsessed shell. It is revealed that the Sheep had also taken control of the Boss as another host, driving him to great power but then discarding the Boss once he accomplished the goal of establishing a society (resulting in the blood cyst that ultimately kills the Boss).

Led farther to an isolated house in a pasture where The Sheep Professor once resided, the narrator and his girlfriend reside for the night with almost half of the month allotted used up. Both discover the supplies left by The Rat and correctly guess that he's still around. The girlfriend is driven away by a figure called The Sheep Man that is later revealed to be none other than The Rat in another form. During a conversation with the narrator, The Rat reveals that he had become The Sheep's next host and isolated himself to prevent any possible harm to others (such as the Sheep possessing someone else). The Rat committed suicide via hanging while the Sheep was asleep inside him, killing it along with him. The Rat then bids the narrator farewell while the narrator later meets with the Boss' secretary who had set up the narrator to flush out the Sheep, knowing that its next host would be The Rat.

Aspects
Physically, the Sheep is described as assuming the form of an unusual chestnut-colored sheep with a star-shaped mark on its flank. But it maintains an enigmatic ambiance as it's never been seen. The Sheep Professor describes the Sheep as "entering" a human host so as to take advantage of their capabilities to fulfill some goal. On one hand, the Sheep drove the Boss to society creation and establishing a great deal of power, suggesting that the Sheep sought to achieve some power in society, barring that it discarded the Boss soon after completing its goal. The Sheep's true intent and goal, however, are never fully made clear.

In his conversation with the narrator, The Rat mentions that the Sheep has control freak tendencies like wanting the entirety of its human hosts, from their emotions to their weaknesses and strengths. In exchange, it seems to grant its host incredible power and an immortal state not held-back by weakness. However, The Rat also hints that the Sheep keeps its hosts in the dark about what they can accomplish, completely controlling their bodies and not letting them truly benefit. It is also described as having tendrils and feelers of sorts that act in a life-draining manner.