Palpatine (Lord Sidious) sends Darth Maul against the Black Sun crime syndicate to make sure that they don't interfere with his plans. Black Sun is under the leadership of one man, with nine "vigos" under him, each controlling a system for the syndicate.
Palpatine Darth Maul
Maul convinces two Black Sun enforcers, Asa and Gargachykk, to take him to see Darnada, their Vigo. They enter just in time to see a Neimoidan from the Trade Federation being ushered out. He was trying to tell Darnada that the Sith have returned and are planning to use the Trade Federation to blockade Naboo, but Darnada didn't believe him. He didn't believe that the Sith had returned. He also mentions that the Trade Federation is owned by Black Sun.
Asa Naga Gargachykk
Maul kills Gargachykk, Darnada, and Darnada's bodyguard, Sinya, but lets Asa live, telling him that another Black Sun Vigo sent him against Darnada.
Sinya with Neimoidian
Darth Maul's second Vigo victim, before he dies, tells him that the Black Sun base is on Ralltir.
On Ralltir, the remaining seven Vigos have assembled to discuss what is happening. They all suspect each other, as if Darth Maul is working for one of them against the others. Master Lex (Alexi Garyn), head of Black Sun, then brings Asa in to tell his story. Lex explains that Maul was trying to turn them against each other, but now they will wait for him to come to them and face him together.
Mighella, Lex's bodyguard, is Force adept. She senses Darth Maul's coming and knows that he's not Jedi, but doesn't recognize what he is.
Maul easily defeats the Vigos' bodyguards and then kills the Vigos themselves as Master Lex seeks to escape. Mighella, a nightsister, witch of Darthomir, stays behind to face him. She lasts longer than the others, but is eventually killed.
Maul catches up to Lex in the tunnels under the base and kills him.