Black X is a criminal organization that acts as antagonist in Red's storyline in SaGa Frontier. Black X is involved in many criminal activites, such as terrorism, smuggling of illegal weapons and drugs, kidnapping and slave labor. Their presence is tolerated by Trinity, the region's government, as Black X supplies them with technology and armaments. Red is after Black X for revenge on the murder of his father, who was investigating Black X and Dr. Klein, who was a former friend of his.
Black X members
- Shuzer - He is one of the Four Emperors of Black X, having his body modified by Dr. Klein with robotic parts. He is responsible for Black X's terrorist activities and assassination. He attacks Red and his father while they are driving, killing Red's father and leaving Red badly wounded. Red is saved by the hero Alkarl, who forces Shuzer to flee and turns Red into Alkaiser. Red investigates Balck X and eventually finds Shuzer's base in the back alleys of Koorong, where they fight. Shuzer attempts to flee by helicopter, but Red follows him and, transformed into Alkaiser, fights him again and defeats him. Shuzer appears again in Black X's base, having been recovered by Dr. Klein, but he once again is defeated by Alkaiser.
- Metal Black - Metal Black is actually a robot built by Dr. Klein. His base is located in Kyo, where is hidden a drugs factory. Though he is a robot, Metal Black learned to value life and respect his adversaries. When Red blows up the drugs factory, Metal Black challenges him as he escapes the place, but ends destroyed. Dr. Klein rebuilds him and leaves him on watch in the Black Ray, Black X's personal ship. Red infiltrates the Black Ray in order to reach Black X's base, but stumbles upon Metal Black, who pursues his inside the ship. The two fight again, but Metal Black activates the self-destruction sequence of the ship. Red and his friends manage to escape the explosion and reach the base. Red, transformed into Alkaiser, confronts Dr. Klein, who shows Alkaiser his final upgrade on Metal Black, who now has all data on Alkaiser uploaded into his memory. Dr. Klein orders Metal Black to attack Alkaiser, But Metal Black asks Dr. Klein to allow Alkaiser to recover, to which Klein reluctantly agrees. Alkaiser defeats Metal Black for the last time, recognizing his prowess and wishing he had used his powers for good.
- Berva - He is one of the Four Emperors of Black X, a big monster who work in the Shingrow region recruiting new members for the organization. He uses the Shingrow ruins as a base, making anyone who wanders the place into new recruits, and turning the weak ones into slaves. Red, who was after Black X in Shingrow, teams up with IRPO agent Doll and finds out Berva's hideout. After a brief fight, Berva flees to the Shingrow Palace where they fight agian, but he ends defeated. Berva appears again in Black X's base, having been revived by Dr. Klein to fight Alkaiser, but he is defeated once again.
- Cindy Campbell - The CEO of the BUCCI brand of bags, she is actually one of the Four Emperors of Black X, using her company as a facade for smuggling illegal weapons. Red discovers a shipment of weapons onboard the Cygnus ship and goes after her for answers. Helped by the IRPO agent Fuse, they interrogate her but are unable to get satisfactory answers. When Red returns to Cygnus, the ship is attacked by pirates sent by Cindy to get rid of all evidence connecting her to Black X. Red is once again helped by Fuse, as they free the ship from the pirates. Later on they assault her building, finally fighting her as she morphs into a spider monster, but she ends defeated. She appears again in Black X's base, having been revived by Dr. Klein to fight Alkaiser, but she ends defeated again.
- Dr. Klein - Once a respected scientist, and a colleague of Dr. Okonogi, Red's father. However, Dr. Klein decided to use his knowledge for evil, eventually becoming one of the leaders of the criminal organization Black X, developing their weapons and doing biological research. Okonogi starts investigating Klein in an attempt to stop his madness, but Klein sends Shuzer to kill him. Shuzer kills Dr. Okonogi and almost kills Red, but the hero Alkarl saves Red by turning him into the hero Alkaiser. Red uses his newfound powers to fight Black X, defeating their Four Emperors and making into Black X's base, where he confronts Dr. Klein. Klein sends his rebuilt Four Emperors to fight Alkaiser, but they are all defeated again. Boss X, the true leader of Black X, annoyed by Klein's successive failures shoves him away and decides to deal with Alkaiser for himself.
- Boss X - the main villain and final boss of Red's storyline in SaGa Frontier. Boss X is a strange creature on a huge robotic body, and the true leader of Black X. His past is a complete mystery. He is fought inside Black X's base, after Alkaiser defeats the Four Emperors sent by Dr. Klein. Annoyed by Klein's continuous failures on defeating Alkaiser, Boss X shoves him away and decides to fight Alkaiser by himself, but he also is defeated, and with his defeat Black X is ultimately finished as well.
|“||I am the real Master of Black X. I control everything. I rule every region. You shall die!||„|
|~ Boss X|
|“||You idiot, this is your chance to beat him for good, and you're philosophizing about fairness? You'll never be the best with that kind of an attitude.||„|
|~ Dr. Klein|
- In Lord of Vermilion, Metal Black makes his additional appearance. He is voiced by Sho Hayami.