iobhan McDougal was the first-born child of Garrett McDougal, the patriarch of an old Gaelic clan that has occupied an island midway between Scotland and Ireland for a thousand generations. On that island is Castle Broen, where first-born McDougals undergo a ritual to prove themselves worthy to lead the clan. When Siobhan was young, she traveled the world, only returning to Castle Broen when she heard of her father's death. Her uncle Seamus determined that no woman would lead the clan and intended her brother Bevan to become the new patriarch. She went ahead with the family ritual by herself, which involved calling on supernatural forces for power. She was interrupted by Bevan, and the distraction proved disastrous as she was dragged away into an infernal netherworld. An entity called "the Crone" granted her powers and the ability to return to Earth as the Silver Banshee, but demanded payment in the form of an occult book that belonged to her father. She found that her father's book collection had been shipped off for sale in the United States. Her quest brought her to Metropolis. Killing anyone that stood in the way of her search attracted the attention of Superman, who was able to defeat her when he realised that she could only kill a person once as she turned away from someone who resembled a previous victim; by faking his death, Superman was able to enlist the Martian Manhunter to attack Banshee by posing as Superman's ghost. Unable to defeat Superman, she chose to retreat and continue her mission at a later date.
Silver Banshee returned to Metropolis twice more, but was halted both times by Superman. It was Batman who finally found the book among some stolen goods in Gotham City. Superman brought the book to Castle Broen where he was confronted by Silver Banshee. The Crone appeared at the castle, and after an enigmatic warning to Superman, she dragged the Banshee, Bevan, and Seamus off to her Netherworld.
In Leesburg, Supergirl rescued Silver Banshee from Satanus' Netherworld when the chaos flow brought the river Styx to the town. Silver Banshee was left in a confused state, eventually going back to her psychotic persona and using Supergirl's friend Mattie as a host while rampaging on the streets. Mattie and Silver Banshee thus proceeded to nearby Schnaffenburg where Mattie tried to get revenge on Gerald McFee, who killed her brother during Final Night while in thrall to Gorilla Grodd. Supergirl calmed Silver Banshee, separating Mattie from her, which led to Silver Banshee temporarily vanishing.
Silver Banshee was one of the final four villains- along with Bizarro, Mongul, and the Master Jailer- sent against Superman by Manchester Black, Black using his powers to make Banshee and Bizarro sane enough to tactically outthink Superman, also granting Banshee awareness of his Kryptonian name so that she could use her magic against him more effectively. Despite this, Superman was able to defeat the four, forcing Mongul to expend his energy before dropping a nuclear-powered superhuman onto the deserted island that they were currently inhabiting.
Silver Banshee attempted to collect the billion dollar bounty President Luthor placed on Superman’s head in Superman/Batman #3, but failed, with Batman using an ultrasonic generator to keep her nullified.
Silver Banshee later joined the Secret Society headed by Alexander Luthor. She was one of the members who turned on Black Adam when Luthor needed him for his machine. She also took part in the Battle of Metropolis.
Silver Banshee battles Supergirl in Supergirl #34, and is expected to be a recurring nemesis for Supergirl, as well as Superman, as part of an attempt to tie Supergirl's book in with Superman's titles.
In Superman #682, Supergirl was used as a diversion as some members of Kandor captured Silver Banshee, placing her in the Phantom Zone. Later, Superman freed Silver Banshee to be taken to Belle Reve.
Inspector Henderson with other police officers break into an apartment, but it explodes and then they find a corpse covered in runes. Kara meets with Inspector Henderson, who's following a case his old mentor was never able to close, and thinks it has to do with items Silver Banshee needs to lift her curse. Inspector Henderson finds his mentor had the item, but it imbeds itself in Inspector Henderson's hand, allowing Silver Banshee to track him. Silver Banshee shows up and fights Supergirl, but Supergirl opens a package from Henderson and becomes possessed by a Banshee hybrid. Banshee-Supergirl and the Silver Banshee battle each other as events are recapped. Supergirl tells Silver Banshee they hid the artifacts in people, in order to keep them hidden from her. Apparently all the items were hidden not as a curse, but as a test for prospective clan leaders. Henderson punches Banshee-Supergirl, which is effective because of the artifact in his hand. Supergirl tries to exorcise the spirits possessing her but fails. Henderson realizes the spirits are tied to the artifacts and can be used against them. He then stabs his hand and breaking Supergirl free from her spirits. Silver Banshee then uses her wails to disperse the spirits. She finally uses magic to remove the artifacts from Henderson's hand and lets him know she is indebted to him.