Unlike the comics, MacDougal's first name in the Arrowverse should be addressed as Agatha instead of Siobhan because it would get us confused with the Prime Earth Silver Banshee Siobhan Smythe who is played by Italia Ricci, who in the comics is one of Kara's closet friends and allies. McDougal as one of Superman's frequent foes is also one of the most ruthless ones he and Batman have fought but here in the Arrowverse just like in the comics she is to appear as one of the villains Superman has fought over the years along with Metallo, Lex Luthor and others he has fought before Kara came to Earth but also that before her first face off with Superman, McDougal's origin is to be similar to the comics where she around her early 20's tried to perform a certain ritual that was interrupted by her brother Bevan which would also here in the show lead her Uncle Seamus into ruining her relationship with a boyfriend of hers in Scottland and having been sentenced to prison for witchcraft but instead of being cursed and killed off just to be resurrected as the Silver Banshee, Agatha is to be turned into the Silver Banshee by the same Banshee that cursed Siobhan and her family and because of how she isn't able to revert back to human like Siobhan does in the comics, she then lashes out at her brother and uncle for interrupting her ritual and kills them both for ruining her life but not after killing her boyfriend who then started hanging out with another woman and kills her too before heading over to Metropolis to find the book she needs to complete her spell and revert to human and banshee form but on the count While many of you DC fans who are watching the series along with the Flash, Arrow, and Legends of Tomorrow, let me give you the run down on some of the Prime Earth counter parts of the DC comic characters that appeared in the CW/Arrowverse so far;
Thomas Merlyn played by Colin Donnell
Cisco Ramon/Vibe played by Carlos Valdes
Caitlin Snow/Killer Frost played by Danielle Panabaker
Siobhan Smythe/Silver Banshee played by Italia Ricci
and Axel Walker/The Trickster played by Devon Graye
These are the five Prime Earth characters that appeared in the shows of the Arrowverse so far and while Tommy and Axel appeared with Malcolm and James Jesse being their fathers (the New Earth versions of Merlyn and the Trickster), and for those who appeared in the shows without their New Earth Counterparts, Cisco appears in the Flash as Barry's friend and most important ally along with Caitlin who is about to turn to the dark side as Killer Frost thanks to Barry's lack of mental maturity that caused him to screw with Time because of Zoom killing his father right in front of him and the Iron Masked prisoner Jay Garrick being his father's doppleganger from Earth 3 hollowing him out, and Siobhan Smythe appeared as Kara's rival and enemy who is yet to make amends with her and be redeemed as a friend and ally later once CW has an episode in season 2 available for Italia to reprise her role at a perfect time where the people of ABC take a 2 to 3 week break from filming more Designated Survivor episodes or at least get all the episodes of season 1 done in time before CW wraps up filming all remaining Season 2 episodes so that the CW should be able to have Italia reprise her role as Siobhan Smyrhe for the two final episodes so that she can team up with Supergirl against the Silver Banshee, Agatha MacDougal if they do make sure that Ricci's character will still be here after Barry Allen's tampering with the timeline left ramifications after creating Flashpoint and before Eobard fixed it but of course she will return to the series either way.
Now for the original Silver Banshee that CW should have lined up as the main antagonist along side the doctor running Project Cadmus in Supergirl season 2, Kriesberg should have her act as a dark toned villain and just like Zoom, Damien Dark, and Deathstroke.
Agatha McDougal is to be ruthless, impulsive with rage , volatile, insane, and attempts to take vengeance on Superman by killing Kara or tearing their lives apart while she still struggles on getting her humanity back with a new spell book that may regard members of Siobhan's family being part of the ritual she needs to complete the spell she needs to cast that will make her human again or be able to revert to human while maintaining her supernatural form and abilities and because she is able to merge with humans and take control of them like puppets, there is slight speculation to this theory that should be factored into the show that she may have been responsible for making Siobhan go through all the trauma she suffered since she was 17 with her father's affair with his assistant but also because of how the setbacks from her past made her envy Kara and Supergirl, there would also have to be something else that would have made her act mean to Kara than just one incident that maybe sometime after or before she caught her father cheating that she may have once had a boy friend that she dated for 2 years that her relationship with him ended because she caught him hooking up with a blonde girl in the hallway which broke her heart which probably why Winn's intervention with her vendetta against Kara hurt her so badly that it ended up triggering the curse that his act against her decision hurt her so badly that other than defending the woman Siobhan was upset with for making her lose her job at Catco that it made him remind her of her boyfriend. Other than Winn not letting her get even with Kara because of her being his best friend, he wasn't being specific and supportive enough to Siobhan on how she should move pass the setback she went through. While it is unclear to how Winn found out about her attempts of making Kara lose her job through email fraud, it is quite possible that Agatha might have been stalking Siobhan while she snuck back into Catco and watched her try to get Kara fired then ratted her out to Winn while merged with his co-workers knowing that having him act against Siobhan's attempts of making Kara get fired would hurt her enough to trigger the curse that by doing so, not only would she end up being her pawn at killing Supergirl but also with Winn having to be the one that wronged her, Agatha would also abduct him along with most people in her family and use him to help her make the spell she needs to regaining her humanity to work.
And while the people from Project Cadmus are mentioned to be the main antagonist in the first half of season 2, MacDougal is to cameo in the mid season finale either working with the lead doctor of having merged with her and using her to make all other officials in Cadmus carry out her demands that after all the years she's been stuck living most of her life as a banshee, Agatha throughout the second half of season 2 just like Zoom will stop at nothing to making sure she gets her humanity back and no matter how many lives she destroys just to get it
how many people she kills just for getting in her way and to make Superman and Supergirl suffer
even if she has to kidnap James Olsen and Lucy Lane to make them Project Cadmus' experiments that would grant them their powers which would make them become heroes in the future
and incase all else fails after Eradicator and Cyborg Superman are subdued, she will kill Supergirl or someone close to her if she has to rob the will and hope out of her and everyone else so that she won't be abrupted from kidnapping members of the Smythes family and Winn to help her conduct her dark magic ritual of regaining her humanity back at her castle in Scotland, even if she has to use the head doctor to order Cadmus to unleash Doomsday on the DEO to wipe out or keep most of them along with Martian Manhunter and Miss Martian and Superboy and Superman busy by having him trash Metropolis so that things go according to plan.
Of course in the penultimate episode of the new season that won't stop Siobhan from escaping the prison she is kept in using her sonic screams to teleport out of the cell and over to her Aunt's shop where she will explain to her everything that she knows about Agatha and their history and what the scottish banshee told her on everything she did. But as soon as Siobhan was about to hand herself over to the officers who came by the call of the customers that ran out of her aunt's store, Agatha (merged with one of the cops who is 15 ft away from the others) kills them all with her screams right in front of SIobhan (immune to the loud noise thanks to her powers from the curse) aslo saw that cop who was screaming at the others had his eyes red as MacDougal comes out from the cop who she then kills him before she turns her attention SIobhan who then realizes at that moment that she was the one causing her all the trouble 7 to 11 years ago and with her powers having grown over the last year, Siobhan will be able to put up a fight with Agatha long enough until the DEO shows up leaving MacDougal to escape with Sinead leaving Siobhan more distraughted that more people in her family are being taken. For even more info on how CW is to determine MacDougal's fate in the season 2 finale, be sure to read the next article on how they are to do the plots of the final 2 episodes.