Jack

Jack (ジャック) is a quaternary antagonist from Mega Man Star Force 3. He is the younger brother of Queen Tia, and both work for Dealer. The FM-ian Corvus is, along with Virgo, the most wanted criminal on Planet FM. He also has something of an axe to grind with Omega-Xis. Jack and Corvus can perform EM Wave Change to form Jack Corvus, a fire-elemental being who can attack from the skies. He enters the story as a new transfer student at Echo Ridge Elementary, filling up Pat Sprigs's empty seat in 5-A. He is mostly emotionless around others, his sister being the only one he can open up to, though he does show a highly aggressive side as well. He is in charge of distributing the Noise Cards to corrupt Wizards.

Mega Man Star Force 3
Jack and his sister are were both orphaned in a war sparked over technological advances. As a consequence, he and his sister wish to use Meteor G's power to destroy the world's technology. He and his sister then enter Dealer which he was in charge of, to infect various Wizards with Noise Cards, and collect the Crimson that comes out of the Wizards.

He enters Geo's school to pose as a new student. This is a facade and over the course of the game he infects Magnes, changing him into Spades Magnus, Bud, causing him to force an EM Wave Change, Ice, changing her into Diamond Ice, and Strong, changing him into Club Strong, with Noise Cards. At Alohaha he and his sister reveal their true identities then escape when Joker destroys Luna.

After Queen Tia was caught by WAZA, he kidnapped Luna and threatened to kill her to lure Geo out. But with Rogue and Wolf Woods' help they manage to stop Jack Corvus, Jack's wave change form. Later when Satella Police manage to reach Mr. King and Heartless, Jack and Queen Tia appear. Mr. King reveals his plan, then Acid Ace and Grave Joker battle each other and both disappear. Jack and Queen Tia then leave soon after the struggle at Dealer's base ends, due to having plans of their own.

Jack eagerly follows his sister's ambition to destroy the Earth using the accumulated Noise power inside Meteor G to destroy the Earth. As Jack Corvus, he and Queen Virgo confront Mister King but because of the waveout ring, they were trapped. Heartless then reveals her true identity as a WAZA spy (not truly confirmed at that point in the story) and trapped Mr. King instead, allowing Jack and Queen Tia to enter Meteor G.

Inside Meteor G, he fights against Mega Man and loses, ultimately being knocked unconscious. He later reappears to help Geo take out his revenge, saying that what they are doing will only destroy, not create, and that they should be the last to feel the suffering of war brought about by EM technology. Corvus, who was scared of imprisonment decided to turn on him, resulting in only Corvus to be deleted by Rogue. After that they leave Meteor G, with Jack asking Geo if they can have fun together like before when he returns, to which Geo accepts.

After Meteor G had been destroyed, Jack and Queen Tia, with the help of Solo (who only wanted to finish his fight with Mega Man), use the technology left behind at Dealer's old base to help guide Geo back to Earth. During the end credits, he is seen celebrating with Geo, Luna, Bud, Zack, Sonia, and their Wizards at a party.

Trivia

 * Jack bears a strong resemblance to Prometheus from the Mega Man ZX series, as both of them have aggressive personalities as well as both making use of the fire element. They also share a female sibling of calm and cold nature, and also follow the instructions of a "king". Jack serving Mr. King, while Prometheus serves Albert, who calls himself a king. In addition, both Jack and Prometheus made plans to betray their masters (Mr. King and Albert, respectively), for reasons relating to their torment under their masters.
 * Jack shares similarities with Dark Scythe from Mega Man Battle Network 6 due to the fact that both of them are part of the the same school of the protagonists. Both are stoic and shows enthusiasm for violence.
 * It is possible that Jack has feelings for Luna Platz. This is evidenced as after Jack revealed his identity to Mega Man, and Luna had come, he immediately turned around, as if he didn't want her to see him. He was also shocked when Joker destroyed Luna, which may have caused him to be more rash and violent, and thereby removing him from the attack on the Satella Police. Also, when Jack attacked the school, he was shocked to see Luna being alive, and was hesitant at first to attack.
 * It is possible that Jack began opening up to the others because of Luna, as she had always tried to get him to join their activities, much to his annoyance.
 * Luna has also shown to have great care for Jack, as she continuously show concern and worry for him when she saw him as Jack Corvus and kept trying to reason with him when he attacked the school. However, when Jack was about to launch his attack, Luna was in disbelief as she knew that Jack wasn't going to stop.