Codename: Banshee
Real Name: Sean Cassidy
Height: 6'0"
Weight: 170 lbs
Group Affiliation: Generation X (teacher and headmaster)
Previous Affiliations: Factor 3, X-Men
First Appearance: Uncanny X-Men #28
Known Relatives: Maeve Rourke (wife, deceased), Theresa Rourke (daughter), Black Tom Cassidy (cousin, deceased)
Known Allies: Moira MacTaggart, Forge, Professor Charles Xavier, Emma Frost
Known Enemies: The Ogre, Black Tom Cassidy, Juggernaut, Moses Magnum

Powers: Banshee has the mutant ability to create a sonic scream which he can use in a variety of different ways. Flight, hyponisis, and basic destruction have been varieties of his power. There have been many times when Sean has spoken while he uses his sonic scream, but that is theoretically impossible unless he has two throats (which might be the case with his daughter, Theresa).

Origin: In one of the first uses of his mutant power, young Sean Cassidy saved the life of the beautiful Maeve Rourke. Shortly after, Maeve and Sean were married. However, Sean was pulled away from his dear wife by Interpol. During a raid, Maeve was killed, but was able to give birth to a little baby girl: Theresa Rourke. Her "uncle", Tom Cassidy, took her and raised her as his own daughter, never telling her about her father, Sean.

Still unknowing about Theresa, Sean joined up with the New York Police Department. He also met a young Emma Frost for the first time when he confronted the Dark Beast. He would not see Ms. Frost until years later, when she was the White Queen of the Hellfire Club. Anyway, Sean did find out about his daughter, but thought she was dead. So, he went a little wacko and became a petty thief. Later, the Ogre took over his mind and forced him to join Factor 3. Banshee got over the mind control and later joined the X-Men in order to save the original X-Men from Krakoa. On the "New" X-Men's first mission, Banshee and Thunderbird were on Baron Nefaria's jet. Sean attempted to get Thunderbird off the plane, but it exploded with T-Bird on it. Sean felt responsible for the tragedy, but Cyclops told him that he couldn't have helped one whose pride outweighed his common sense.

Banshee continued to be an asset to the X-Men, until a battle with Moses Magnum. In order to stop the villian, Banshee was forced to push his powers to the limit. The limit was too far and caused him to lose his powers for a long while. During this time, Sean still remained with the team, facing menances like Arcade, Alpha Flight (they aren't really menances, but were attacking the X-Men) and Proteus. After Proteus was killed by Colossus, Banshee stayed at Muir Island with his lady love, Moira MacTaggart, to comfort her after her two losses (her son (Proteus) and husband (Joe MacTaggart)). After the Morlocks were deciminated by the Marauders, they were located to Muir Island. Short after the Fall of the Mutants, the Reavers tried to kill Banshee, who was saved by Amanda Stephon, a sorceress. When he was teleported back to Muir Island by Amanda, the Morlock Healer healed Banshee's wound and restored his sonic scream.

After defeating the Reavers, Banshee and Forge decided to search out the X-Men and try to join up with them again. They also noticed a change in the people on the Muir Island Complex. Moira, Legion, and the others began to act mean and dark. The influence of the Shadow King (in combination with Lorna Dane's new mutant powers) caused this change. However, it was only temporary and was resolved with the defeat of the Shadow King by Professor Xavier. So, Banshee joins up with the X-Men as a reserve member.

Banshee doesn't do much for a long while. He goes off and on between the X-Men and Moira until the Phalanx invade the mansion. As one of the four remaining occupates of the X-Mansion, Banshee is forced to destroy Professor Xavier's files as well as part of the mansion, to protect the next generation of mutants from the Phalanx. With the help of Sabretooth, Emma Frost and Jubilee, Banshee is able to rescue the new mutants, with the exception of Blink, who "died" saving him from Harvester.

Per request of Professor Xavier, Banshee took the job as headmaster of Generation X (along with Emma Frost, the former White Queen). He's been able to bond to all the students, even Penance. In fact, Sean tried various languages to try and speak with Penance, his silent, diamond-hard student. Banshee was attacked by Omega Red on the night of Mondo's induction into the school, with his "soul" stolen by the Russian mutant assassin. Emma had to keep Sean's mind intact, while her students (Generation X) tried to find Omega Red. Chamber was the only one left after Omega Red found Generation X and managed to beat the Russian. With his soul back in his body, Sean continued to school his new mutants. He had been able to keep his students safe until his cousin, Black Tom Cassidy, resurfaced. Kidnapping the Generation X-ers and sending them into the middle of nowhere, Black Tom was ready to kill Banshee unless Sean killed Emma. Refusing to so, Emma took over Sean's mind and forced him to use a sonic scream tha t would make it look like he had killed her. Black Tom was fooled, and later killed by Penance. In the med lab, Sean placed Emma's body on a med-table. It turns out that she wasn't dead, but was able to make Banshee's scream make her unconcious. Lucky Emma.

In an attempt to find out where their students were, Emma mindscanned Banshee for a clue. The way that Black Tom had Generation X arranged was identical to the way Krakoa had the original X-men arranged. So, the two headmasters headed for Krakoa's last location, where they found a ship. No one was on it, so the two headed for Colorado, where the X-Men were being attacked. They were too late, so Banshee and Emma tried to find a safehouse to stay at. In Florida, Emplate confronted them with a bargin: the location of the students for Penance. Emma was planning to trade Penace (she wasn't going to, though), but Sean stopped her and ordered her never to go back to the Academy again.

Banshee takes Penance back to the Massachusetts Academy, where the rest of his students are. Then, he heads for Muir Island in order to get a clue what had happened to M (who was now two little girls). He and Moira had a reconciliation, reviving a bit of their old relationship. After getting the test results, Sean headed back to the school, where Emma promptly punched him in the face.