Mello intends to beat Near and catch Kira, but needs a Death Note to do so. He joins the Mafia led by Rod Ross, who wants to increase the Mafia's influence. By allying together, Mello profits from the Mafia's resources and Rod Ross profits from Mello's intellect. Having proved his usefulness by killing a rival gang leader that "even Kira couldn't catch," Mello becomes a primary member, with Ross taking Mello's advice.
They eventually get their hands on a Death Note by kidnapping Sayu Yagami, and asking for the notebook in exchange for her life. At an underground bunker, they give Sayu to Soichiro Yagami, who hands over the Death Note. The notebook is then loaded onto a missile that cannot be tracked by radar to send it elsewhere. Having recovered the notebook, Mello orders the death of all but four members of the SPK.
Sidoh, who has been searching for his Death Note, eventually arrives at the Mafia's hideout. Sidoh identifies Jack Neylon as the current owner of his Death Note, and takes it out of Mello's hands before dropping it onto Neylon's head. Neylon becomes terrified upon seeing Sidoh, and tells everyone to touch the notebook. Upon doing so, the other members view Sidoh, and begin to shoot at him. The bullets do nothing, of course. Sidoh strikes up an alliance of sorts with Mello, who tells him that the two rules written in the back of the notebook are false.
Mello subsequently instructs Sidoh to guard outside the base should there be any attackers, and this proves useful when Sidoh removes the helmets of attackers led by Yitzak Ghazanin, allowing Jack to write in all their names, using the Shinigami Eyes.
After this incident, the mafia switches bases. Kira hands over the notebook to the Task Force and instructs them to raid the mafia base, with him managing to learn the address by controlling multiple members of the mafia to mail him the address. The cue for the Task Force to attack is the deaths of the majority of the mafiosi, including Rod Ross, only for more deaths to occur from the attack.
Mello eventually has no choice but to blow up the base, most likely killing any few remaining members.
The Mafia has several hideouts. A previous hideout that was used two years prior to the story is stated to be under SPK surveillance, following the Mafia's involvement in the Kira case.
The hideout that is first and primarily seen appears to be a factory or industrial plant of some sort, located in Los Angeles, California. The outside has several ladders and pipes on it, as well as a few staircases. This is the hideout that Sidoh arrives at in his search for his Death Note, as well as the first hideout to be raided by the Japanese Task Force.
The second hideout is used after the previous one is raided by the Task Force. The hideout appears to be a large, Victorian-style building, furnished with seemingly expensive items. Many important events take place here. This hideout is raided by the Task Force, with Soichiro Yagami having the Shinigami Eyes. Nearly all members of the Mafia subsequently die, Soichiro is mortally shot, and Mello escapes being captured by setting off a large bomb.
The Mafia also has an underground bunker located in the desert. The bunker was used as the location to make a trade with Soichiro Yagami for the Death Note, in exchange for his daughter Sayu Yagami. The bunker appears to be a long tunnel-like structure. It has two openings; one which is used by Soichiro to enter and exit, and another which Sayu's kidnapper used to leave. Within the bunker is a revolving bulletproof door, used to exchange Sayu and the Death Note. The location also has a nearby base to launch a missile, which the Mafia use to transport the Death Note without being traced by radar.
|Rod Ross||Rod Ross is the head of the Mafia, though he primarily follows Mello's orders.|
|Jack Neylon||Jack Neylon (real name Kal Snydar) is the owner of Sidoh's Death Note after it is given to them by the Japanese Task Force. After Sidoh tracks down his Death Note, Jack is ordered to perform the Shinigami Eye Deal and consequently gains the power of the Shinigami Eyes. Light Yagami uses his own Death Note to have Neylon mail him the address of Mello's hideout.
In the anime, the Eye Deal and first raid attempt are cut.
|Zakk Irius||Zakk Irius is used by the Mafia to converse with the Japanese police at the airport. The organization kills Irius after he guides Soichiro to the correct aircraft. He dies from a heart attack when the airplane lands; his crew wrote his name into the Death Note.|
|Glen Humphreys||Glen Humphreys and Rashual Bid are veteran gang members said to be the main force behind Ross. They are seen at the Mafia's hideout by satellite confirming its location; this behavior was presumably manipulated with the Death Note by Light as an excuse for how he had discovered their true whereabouts. Rashual was killed by the Death Note during the raid by the Task Force members. Glen is killed by the Death Note prior to the police raid. Humphreys is known as Gurren Hangfreeze in the Japanese version and their real names are Ralph Bay & Al Meem respectively, or Langford Bid & Yale Mison in Japanese.|
|Miller||Miller (real name Andrew Millar) is a member who is killed by "Y462" as a test subject during the exchange to determine whether the Death Note is real. He is killed because he was stealing drugs from the gang to sell, and is described as an "incompetent guy."|
|Jose||Jose is not affected by the Death Note when the other members are killed, as only his alias is known. He fakes being dead and fatally shoots Soichiro, then dies when the rest of the Japanese Police enter the room and shoot him.|
|Roy & Skyer||Roy and Skyer are not affected by the Death Note, which kills the other members, as only their aliases are known. They attempt to retrieve the Death Note, but the Task Force disarms and subdues them both. They presumably die later on when Mello detonates the explosives which destroy the entire building. It's believed that ownership was transferred to one of them after Snydar dies only to be lost upon their own deaths.|
|"Y462"||"Y462" (real name unknown) makes the exchange with Soichiro Yagami for the Death Note and is the one to kill Miller. He holds ownership of the notebook for a short time but is killed by a remote explosive planted in his helicopter after he loads the Death Note onto the missile. His death causes ownership of the Death Note to be passed on to Kal Snydar, the first one to touch the notebook after he dies. Rod Ross had falsely promised that making the exchange would redeem him of his past failures.|
|Pedoro Kollet||Pedoro Kollet (alias unknown) interrogated Kanichi Takimura. Though Takimura is left in his custody, Kollet dozes off while watching him. During this time Takimura kills himself, as was written in the Death Note.|
|Eddie||Eddie, along with Kollet, is tasked with interrogating Takimura and keeping an eye on him.|
|Ill Ratt||Ill Ratt is an SPK member passing along information to Mello.|
|Greg Parker||Greg Parker is in charge of buying the groceries of the group and is discovered by Kanzo Mogi after buying several bars of chocolate from the same brand.|
|Beck Wallese, Danny Bloyer, Seam Solt, Andrew Miller, & Sonny Hound||Beck Wallese (real name Billy Morgan), Danny Bloyer (Robert Rangdon), Seam Solt (George Michel), Andrew Miller, and Sonny Hound are members seen on the list of Mafia members Misa Amane searches through to find the current Death Note owner. They are listed next to Jack Neylon's (Kal Snydar's) name.|
|Unnamed members||There are other unnamed members of the Mafia who are killed after the Mafia obtains a Death Note due to Ross and Mello killing their underlings and subordinates and leaving only a chosen few. Mello also has several Mafia members use the Death Note before Ross does in order to learn whether or not the 13 Day Rule is false.|