The Battle of Shumari represents a significant clash. It involved surviving Jedi from Order 66 and the forces of the Galactic Empire on the world of Shumari.
The planet was under siege by the Empire, which deployed several Star Destroyers into its orbit. These ships unleashed a powerful orbital bombardment upon the surface. Simultaneously, a ground battle raged between the Jedi and a vast Imperial army composed of various stormtroopers, all under the direct command of Darth Vader. Vader personally eliminated numerous Jedi, while others succumbed to stormtrooper blaster fire and the devastating planetary bombardment.
During the heat of battle, a Sullustan Jedi located Vader and alerted a group of fellow Jedi warriors. This group included a Human Jedi, a Gran Jedi, a Twi'lek Jedi, and Tao, among others. The Jedi group immediately engaged Vader in combat. However, the duel proved to be brief, as Vader swiftly overpowered all except the Human Jedi and Tao.
Witnessing the deaths of his comrades, the Human Jedi vowed revenge against Vader and launched an attack. Vader, however, effortlessly countered the Jedi's assault, killing him with a decisive blow.
In the end, all the Jedi perished, with the exception of Tao. Shumari was left utterly ruined by the intense planetary bombardment, rendering it uninhabitable. Vader, sensing the anger within Tao, spared his life and took him on as his second secret Sith apprentice.
Vader and Tao later revisited the devastated planet in 1 ABY. It was there that Tao would ultimately save Vader's life, only to succumb to fatal injuries shortly after.
This particular battle is depicted exclusively in the story Perfect Evil, which was published across the issues Black and Silver of Star Wars Manga. Originally created in Japan, Lucasfilm initially considered these stories to have "fuzzy" continuity. Later, the stories were republished in English in the United Kingdom under the Infinities label, which designated them as non-canonical. Subsequently, the planet Shumari was mentioned in The Essential Atlas, with the Shumari system appearing in its appendix. However, according to Jason Fry, its inclusion should only be considered canon for the geographical information provided, and not for any other details from the story.