Siobhan McDougal was the first born child of Garrett McDougal, the patriarch of a clan of old Gaelics that resided on an island halfway between Ireland and Scotland. The clan had remained stationed there for a thousand generations. The island held the Castle Broen, the battleground for the first born McDougals to battle for the honor of leading the clan. It was a ritual as old as the clan. It was extremely important to all who reside on the island and one Siobhan only paid heed to as part of her family lore.
She left her clan at an early age to travel the world. She had grown tired of life with the clan and needed an escape. She had remained away for an extended period of time and only returned when she received news that her father had died. Upon her return, the proceedings for the next ritual were already underway. She was told by her uncle Seamus that she was not to take part. He didn't want a woman to be clan leader and had already decided her younger brother Bevan would take her role in the ritual.
Siobhan took this as an affront and decided to do the ritual herself, alone. The ritual involved calling forth supernatural forces for power. She almost succeeded but her brother Bevan inadvertently interrupted her mid-ritual to disastrous effect. The forces consumed her and drug her into the Netherworld.
In the Netherworld, an ancient being known as the "Crone" granted her power and a means to return to the land of the living as the Silver Banshee. She demanded repayment in the form of an occult book that had belonged to her father. Upon her return to her clan, she discovered her father's books were shipped off to the States to be sold. Thus her journey brought her to Metropolis. Not one to be delayed, Silver Banshee killed any and all who stood in her way of finding the book. This drew the attention of Superman, who tried to stop her. She had a leg up however as one of his weaknesses is magic. Their battle was fierce, but she was still unable to defeat Superman so she fled and left the mission to find the book for another date.
Refusing to completely abandon her quest, she returned to Metropolis twice more and faced Superman both times. Just as before, she was defeated by Superman both times. It wouldn't be until much later when Batman discovered the book among other stolen goods in Gotham City that Silver Banshee would take up her quest again. She faced off against Batman when he brought the book back to Castle Broen. She may have stood a chance against Batman but the Crone showed up again and dragged Silver Banshee, Bevan, and her uncle Seamus to the Netherworld.
When the River Styx was brought out of the Underworld and into the town of Leesburg, Supergirl rescued the Banshee from Satanus. This left Silver Banshee confused and she reverted to her psychotic state. She even went so far as to use Supergirl's friend Mattie as her new host and rampaged on the streets. The Mattie possessed Silver Banshee then went to General McFee who was responsible for the death of her brother during the Final Night fiasco while under the control of General Grodd. Supergirl tried to calm the Silver Banshee before she could kill McFee and it worked, separating Mattie from the Banshee. The separation led the the temporary vanishing of the Banshee altogether.
Silver Banshee has since turned up attempting to collect the billion dollar bounty Lex Luthor placed on Superman's head. Once again she lost in her battle with Superman. She then joined the Secret Society led by Alexander Luthor. She was one of the members who turned on Black Adam when he was needed for a machine Luthor was building. She then took part in the Battle of Metropolis. Most recently, she has become a nemesis for Supergirl.
Silver Banshee has been kidnapped by citizens of the Bottled City of Kandor and exiled to the Phantom Zone along with other enemies of Superman. Superman rescued her from th Phantom Zone and placed her in Belle Reve.
Inspector Henderson with other police officers break into an apartment that explodes moments later. They find a corpse that is covered in runes. Kara meets Inspector Henderson, who is trying to close a case his mentor never could. He believes the case has to do with items the Silver Banshee has stolen to lift the curse. The Silver Banshee is able to track Inspector Henderson from one of the items that is imbedded into the palm of his hand and was in the possession of his mentor. Supergirl shows up to battle the Silver Banshee is when Kara opens a package from Inspector Henderson she is possessed by a Banshhe Hybrid. Kara explains the artifacts were hidden in people to keep them hidden from the Silver Banshee. The items were not hidden as a curse, but for prospective clan leaders. Henderson punches the Supergirl Banshee because of the artifact in his hand. Supergirl attempts to exorcise the spirits from her, but fails.
Henderson realizes the spirits are tied to the artifacts and stabs his hand. Supergirl is no longer possessed by the spirits and the Silver Banshee uses her wails to disperse the spirits.
She uses the magic to remove the artifact from Henderson's palm and lets him know she is indebted to him.
The New 52
Siobhan Smythe arrives to New York, in order to leave her past in Ireland behind. Her mother and father died when she was very young. While in Queens she comes face to face with Supergirl. Siobhan understands Kara's kryptonian language and escapes the local authorities with her help, which leads to a friendship between the two, both girls figure out that they need each other in hopes of survival. Eventually Siobhan's father, The Black Banshee, attacks the two girls, which causes Siobhan to reveal herself as the Silver Banshee. This leads to a battle between the two girls versus Siobhan's father.
Powers and Abilities
Sliver Banshee possesses an array of superhuman attributes which includes superhuman strength, speed, stamina and endurance. She has also a high resistance towards physical and energy attacks. Sliver Banshee also has a sonic scream which can kill anyone who hears it as long as she knows their true identity. She also uses her sonic scream for other purposes, her teleportation is an example of this. In the New 52 she's shown to master any form of language even animal communication with minimal exposure. However she always speaks with a strong Irish accent.
In the DCAU's Justice League Unlimited & the animated film Superman/Batman: Public Enemies, Silver Banshee is capable of flight under her own power. The Justice League Unlimited version can also siphon the life force of her victims aging them in mere seconds.
In Season 9 episode, "Escape", the Silver Banshee was cursed and banished to the underworld. She later possessed Lois Lane's body and attacks Clark with her sonic scream. She is defeated when the portal that allowed her to escape the underworld was destroyed by Chloe by throwing it into the fire.
Justice League Unlimited
Silver Banshee appeared in the episode "Chaos At Earths Core." She and Metallo and Skartaris were changed with the task of collection Kryptonite. Captured by Green Lantern, Silver Banshee escaped and it is later revealed that she is a member of the Secret Society.
Superman/Batman: Public Enemies
Silver Banshee is one of the many villains that attack Superman and Batman to
receive the $1 billion bounty that Lex Luthor placed on Superman's head. She is defeated by Superman when he takes her into the upper atmosphere where she can't breathe.
Silver Banshee has appeared in several Superman games, including Superman: Shadow of Apokolips, Superman: Countdown to Apokolips, and Superman: The Man of Steel. Throughout these appearance's she was voiced by Kim Mai Guest.