Former lover of Goliath and former member of the group. She originally distrusted humans but now lives for the destruction of humanity itself. She still has feelings for Goliath but sees his feelings for the humans as his greatest weakness.
Demona spends the entire series caught in a tragic yet fitting psychological trap of her own making. Episodes often show that her raging hatred of humans is how she avoids admitting to herself that her own treachery killed off most of her clan (at one point, she turns her self-recrimination into hatred of humans with the roar, "What have I done -- no, what have THEY done?"). Since the only way she can deny her guilt is to scapegoat humanity, she will lose this protection from her guilt the moment she succeeds at killing off humanity -- so she often unconsciously self-sabotages her schemes with recklessness, gloating and daring Goliath to to stop her, and leaving loopholes for her own defeat without her realizing it.
Demona was hatched in 938 in Wyvern in Scotland in the same rookery as Goliath, Desdemona (Coldfire), Othello, Iago and Hyppolyta. Demona and Goliath fell in love at a very young age. Demona was also a very unusual gargoyle as she had a keen interest in magic and she was taken as an apprentice by the Archmage.
In 975 Demona's apprenticeship to the Archmage came to an end. He enlisted Demona to steal a magical item called the Phoenix Gate which she did but was soon greeted by a time traveling version of her future self her warned her of the destruction that awaited her if she continued on her path. The older Demona also tried to convince her younger self to use the gate to destroy all humans. The young Demona was horrified by her future self and hid the gate from the Archmage. He was so furious that he ended their partnership.
Despite this warning from her future self Demona grew increasingly bitter of the treatment of her species and became to conspire against the humans in castle Wyvern. Despite her hatred of the humans Demona saw the Captain of the Guard as an ally and the two became to plot.
They eventually planned for Hakon of the Vikings to take Wyvern from Katherine by convincing Goliath to take the entire Wyvern clan out in force looking for Hakon. Goliath however took only Hudson with him and with Hakon due to attack at dawn, Demona was left in a terrifying position. If she spoke up told the clan what she had done she could be exiled and if she didn't the clan could be destroyed. In the end she trusted the Captain of the guard to protect her clan but just to be safe she flew to a nearby cave so at least she would safe when the sun came up.
When she awoke the next night she was horrified to discover that her clan had been destroyed by Hakon and when Goliath returned to the castle she was too ashamed to face him and hid.
When she finally got the courage and had come up with a cover story she decided to face Goliath but by that time he had been permanently been turned to stone by the Magus.
Demona was grief stricken, she had lost everything. For a moment she became to contemplate her actions and looked as though she was going to take responsibility, she quickly forced that down and swore vengeance of the human race.
After the Wyvern Demona survived by pillaging small farms. In one such farm she attacked a small boy called Gillecomgain permanently scarring him. Gillecomgain swore vengeance against Demona and her entire species and she had done to the human race only years before.
By 1020 she had formed a small clan of six gargoyles. She was the leader and the only female. Gillecomgain now a grown man plagued her as the "Hunter".
The Weird Sisters had been employed by the Archmage to manipulate Macbeth and Demona. The sister's appeared to Demona as three elderly female gargoyles and urged Demona to attack Gillecomgain at Castle Moray the home of Macbeth. When Demona arrived Gillecomgain was trying to assassinate the young Macbeth. Demona fought Gillecomgain and saved the young Macbeth and his future bride. Perhaps seeing something of herself and Goliath in the fledgling couple.
Over a decade later Macbeth and Demona were again manipulated into fighting Gillecomgain together and managed to kill the first of the hunters.
King Duncan was afraid that Demona and Macbeth would ally against him so he attempted to destroy Demona's clan. Demona and Macbeth were finally convinced that they needed her each other. The Weird Sisters set the term of the alliance. For Demona's help against Duncan, Macbeth with give her his youth. The sisters reversed the ages of Demona and Macbeth and made them immortal unable to be killed by any other being except each other, though both were unaware of this at this time.
Together Demona and Macbeth defeated Duncan. Duncan's son Canmore swore revenge on Demona and Macbeth after his father's death. Demona's clan moved to Castle Moray and Demona became Macbeth's chief advisor.
The alliance came to end when Demona overheard Macbeth being counseled to betray her. Macbeth rejected the idea but by that time she had already left. Conspiring to destroy him just as she done decades before at Wyvern.
Demona decided to abandon Castle Moray when a grown up Canmore attacked. Demona's plotting this time around had same success as her previous plans at Wyvern and her new clan was destroyed. Canmore defeated Macbeth fatally wounding him and Demona due to their link. It was at time the two realized that they were immortal. Demona fled Scotland.
Demona's activities are not fully disclosed for the next 900 odd years. Its known that Macbeth and a new line of hunters continued to plague her but even with their interference Demona was still able to obtain two mystical artifacts the Medici Tablet and the Praying Gargoyle.
In the 1980s Demona entered into an alliance with David Xanatos with the aim of freeing the survivors of the Wyvern clan from the Magus's spell.
The spell was finally broken when Castle Wyvern was raised on top of the Eyrie Building. Demona pretended to the newly awakened gargoyles that she had also been under the spell. With the help of New York detective Elisa Maza the clan saw through this ruse and turned on Demona.
Demona spent all of time after this trying to either convert or kill the survivors of the Wyvern Clan now calling themselves the Manhattan Clan. She used both sorcery and technology to do this but repeatedly failed. In one scheme she captured the fae Puck and tried to use him to destroy the human race. Puck repeatedly tricked her but in end he awarded her "entertaining" him and gave her the ability to turn human in the daylight. Originally disgusted by this Demona used her human form to create the identity of Dominque Destine and added even further to her wealth.
The Archmage's plan was later revealed and the Weird Sisters took Macbeth and Demona too Avalon and used them as weapons against the Avalon Clan. This was the first time Demona met her children but cannot remember as after the Archmage was defeated the Weird Sisters put a spell over her to make her lose her memory of the events on the island.
Demona wound up in Paris and encountered Thailog and became his mate. She also married Macbeth under the identity of Dominque Destine and then faked his death to inherit his wealth. Macbeth was freed by Goliath and Eliza Maza. Demona also encountered Angela and she later found out was not only her rookery daughter but biological daughter as well.
Demona later attempted to sway Angela to her cause of destroying humanity but failed. When Thailog tried to kill Angela, Demona turned on him. He then revealed that he had anticipated this and had created a new mate called Delilah using Demona's DNA and Eliza Maza's along with clones of the rest of the Manhattan Clan. Demona and Thailog fought and appeared to die in a fire.
On Hunter's Moon it was finally time to use the stolen Medici Tablet and Praying Gargoyle. Demona attempted to wipe out all of mankind again but was stopped by Goliath and the Hunters.