When faced with internal struggles or unanswered questions, Jedi in Star Wars often experience dark visions. These visions reflect their greatest fears and flaws, which Jedi characters must work to overcome as they grow. For example, Luke Skywalker saw Darth Vader in a vision during The Empire Strikes Back; after decapitating "Vader," Luke sees his own face within Vader's broken helmet, emphasizing that anger and a thirst for revenge will lead him down the same path as the Sith Lord. This is Star Wars's first and most striking vision, and other characters have faced similar illusory trials since, including Kanan Jarrus, Anakin Skywalker, and Ahsoka Tano. Out of all these visions, none were darker than Yoda's visionary experience during The Clone Wars Season 6, Episode 12, "Destiny."
Source：https://www.cbr.com/star-wars-yoda-overcame-dark-vision/
