The Empire had placed several Star Destroyers in orbit around the planet and subjected it to heavy orbital bombardment. Meanwhile, a battle was being fought planetside between Jedi and an army of various types of Imperial stormtroopers under the command of Darth Vader. Vader singlehandedly killed several Jedi, while others fell victim to stormtrooper fire and the planetary bombardment.
The Sullustan Jedi discovers Darth Vader and informs his fellow Jedi.
At some point during the battle, a Sullustan Jedi discovered Vader and informed a group of fellow Jedi, consisting of a Human Jedi, a Gran Jedi, a Twi'lek Jedi, and Tao, among others. The group immediately attacked Vader, but the duel was short, as Vader easily defeated all of them except the Human Jedi and Tao.
Having witnessed the death of his fellow Jedi, the Human Jedi swore to make Vader pay for what he had done and attacked him. Vader, however, easily killed the Jedi, using an effective counter attack.
Eventually, the Jedi were all killed, except Tao, and Shumari had been completely devastated in the planetary bombardment and rendered uninhabitable. Vader had spared Tao's life, because he sensed the anger within Tao, and took him as his second secret Sith apprentice.
Tao and Vader returned to the devastated planet in 1 ABY, where Tao would save Vader's life, just before dying from fatal wounds.
This battle only appears in the story Perfect Evil, which spanned issues Black and Silver of Star Wars Manga. Originally published in Japan, those stories were considered to be of "fuzzy" continuity by Lucasfilm. Since then, they have been republished in English in the United Kingdom under Infinities label, which established the material in them as non-canonical. The planet Shumari has been later referenced in The Essential Atlas, which included the Shumari system in its appendix. However, according to Jason Fry, "its inclusion shouldn't be taken as a statement of canonicity for anything except the geography."