"Brought you here, the galaxy has. Your path, clearly, this is." "You know what I'm looking for." "Something lost. A part of yourself, perhaps. That which you seek, inside, you will find."
Anakin and Qui-Gon visit the Dark Side Cave in Yoda's visions.
Hundreds of years before the Clone Wars, the Jedi Minch battled and killed a powerful Bpfasshi Dark Jedi leader, and his energies absorbed into its surroundings, first tainting the passage with the dark side.
Later, during the Clone Wars, Yoda had a vision of the Dark Side Cave during one of his meditations. In this vision, Qui-Gon Jinn guided a nine-year-old Anakin Skywalker into the cave to face his fears, telling him the same thing Yoda eventually told Anakin's son, Luke, many years later.
During the Great Jedi Purge, Yoda realized that proximity to the Dark Side Cave could help neutralize his strong light sideForce signature—thus preventing his detection by the Sith—and took up residence near the cave, living there for the next two decades, through the reign of the Galactic Empire.
Yoda experiences a vision of Darth Sidious in the cave
During the birth of the Rebellion the clone of Starkiller spoke with Yoda briefly before entering the cave to look for the answers he sought. Starkiller inside the cave Inside he was unable to use his Force powers, except for the Jedi mind trick, which he utilized several times. He faced down other clones of Starkiller and had to carefully traverse some deep pits. He made it deep into the caves, and received a vision of the assault on the Salvation. Starkiller exited the cave, and left Yoda still sitting there and watching.
When Luke Skywalker traveled to Dagobah to train with Yoda in 3 ABY, the elder Master tasked him to enter the cave. Luke confronted an illusion of Darth Vader within and defeated it in a lightsaber duel, dipping into the passion of the dark side in the process. It was there that he realized what would happen if he turned to the dark side of the Force. Behind the mask of Darth Vader, he saw his own face. It also presaged the revelation that Vader was, unknown to him at the time, actually his father, Anakin Skywalker.
Five years after Yoda's death, Luke Skywalker returned to the cave. This time, he had a vision of a possible past, one where Mara Jade accompanied Jabba the Hutt's retinue to the Sarlacc. She was able to pull Luke's lightsaber away from him, and Luke was pushed towards the Sarlacc when his vision suddenly ends. While in the cave, he found a beacon left behind by Jorj Car'das.
In 14 ABY, the dark side power of the cave was siphoned by the Disciples of Ragnos. This supposedly removed all of the dark energy, but it presumably returned to its source when the Scepter of Ragnos was destroyed or otherwise somehow regenerated itself. In 22 ABY, Anakin Solo, Tahiri Veila and Uldir Lochett entered the cave after Anakin had a recurring nightmare of becoming the infamous Darth Vader. There, Tahiri encountered a vision of her parents and grandfather, and Anakin faced the manifestations of his own doubts. The two both emerged victorious. Uldir, however, encountered nothing in the cave but vast emptiness.
Heir to the Empire describes how Jedi MasterYoda battled and defeated another powerful Bpfasshi Dark Jedi inside the Cave. But, in Star Wars Insider 98Leland Chee writes that this is no longer considered part of continuity because Yoda had never been on Dagobah before his exile.
In Battlefront II's Dagobah map, the cave is one of several command posts; inside it, players can hear Darth Vader's distinctive breathing sound.