Siryn

Real Name: Theresa Cassidy

Powers: Siryn is a mutant who has the ability to create various sonic effects through the combined action of her vocal cords and limited psionic powers which can only be used in conjunction with the sounds she produces. She inherited these powers from her father, who has the same abilities.

By focusing her sonic vibrations into an intense beam, Siryn creates what she calls her "sonic lance," which can shatter any known solid substance except adamantium and vibranium. Siryn can use her "sonic lance" at a lower intensity to stun people into unconsciousness without doing them injury.

Siryn can use the sonic vibrations of her scream to propel herself through the air. Although it might be expected that emitting sound waves from her mouth would propel Siryn backwards, since for every action there is an equal and opposite reaction, this is not the case. Siryn's psionic abilities cause the acoustic energy to flow behind her. Siryn's psionic abilities enable her while in mid-flight to temporarily stop screaming to speak or to employ her scream to perform other sonic feats.

Siryn can also use her sonic powers as a form of sonar (SOund Navigation And Ranging).

Siryn's vocal cords and the interiors of her throat and mouth are superhumanly tough, so that the intense pressures and constrictions that she produces do not cause her any injury. While using her sonic powers Siryn also automatically and psionically creates a force field which protects her body from the destructive effects of the sound she creates. The force field only protects Siryn against her own sonic vibrations and nothing else, and can only be activated when she is using her sonic powers.

History: Theresa Cassidy was born in Cassidy Keep, County Mayo, Ireland to Maeve Rourke and Sean Cassidy. Shortly after he was married to Maeve, Sean had to leave on an INTERPOL mission, and he could not maintain contact with his wife, who found out she was pregnant after he left. Sean was gone for a pretty long time, more than a year, and she gave birth to baby Theresa in his absence. Unfortunately, Maeve was also killed in a terrorist attack before her husband returned, leaving Sean’s jealous cousin Tom to care for Theresa until Sean came home. When Sean returned, he was devastated to find out his wife had died, but Tom chose not to tell him about the baby, so Sean left home without finding out about the baby his wife had left behind.

Tom raised Theresa like he would his own daughter, as he loved the child dearly, but told her that her father was dead. Theresa was sent to boarding school when she was 12 so she wouldn’t find out about the illegal activities Tom was involved in. When she was 13, Theresa started drinking, and it developed into alcoholism. Tom was arrested by INTERPOL and sent to prison when Theresa was 15, exacerbating her drinking problem. But Tom broke out of prison after meeting Cain Marko A.K.A. Juggernaut, and they took Theresa to San Francisco on a crime spree, where they ran into Spiderwoman and the X-Men. When the rumble was over, Tom told the X-Men his niece wasn’t involved, and they took her to meet her father, who was overjoyed to meet her.

She lived at Muir Island for awhile, where she met Jamie Madrox, aka Multiple Man, and the two of them enjoyed a close relationship for a time. She eventually broke up with Jamie, however, but it later turned out he wasn’t really Jamie at all, but a renegade duplicate. After the Shadow King’s vicious attack on Muir Island, Theresa traveled to the United States to stop her uncle and Marko in the act of yet another criminal event, where she met X-Force, and has been with them ever since.

James Proudstar, code-named Warpath, a fellow member of X-Force, developed feelings for Theresa, and went with her back to Ireland for 2 weeks to help her overcome her drinking problem and straighten out her relationship with her uncle Tom. Theresa managed to quit drinking and became good friends with James, but he cared about her more than she realized, and wasn’t interested in a relationship with him until after he met Risque, who loved him but betrayed him. After Sam Guthrie A.K.A Cannonball left X-Force and joined the X-Men, Theresa became the deputy leader of the team, which meant very little until Cable and Domino left X-Force, making Siryn the new leader.

Siryn led the team for some time, dealing with a bit of disrespect from a few of her teammates who couldn't see the logic in Siryn=leader, but nonetheless keeping the team together and safe. Domino returned to the team at the same time as Jesse Aaronson invaded, and relieved Siryn of the leadership responsibility.While X-Force was battling the New Hellions, led by Jesse Aaronson's brother, Christoper, Theresa was attacked by former teammate, Feral, and her vocal chords were ripped out. She then left the team, and moved in with her cousin (on mother's side), Victoria Donnelly. However, that didn't last long before she was possessed by the mind of some weird old woman and flew off.