Eve

Not much is known about her to date. Eve was an entity that was cast into the pits and deepest bowels of a realm called Purgatory but she got released by Dragons, arrived on Earth, with a young virgin girl as a vessel. She was part of existence before Angels were, which gave her an advantage over them, being able to inhibit them from using their supernatural powers. She created the Alphas, which were the first monsters of their allotted kind. She, just as of recently, created a worm-like creature which Dean dubbed the "Khan Worm". She also just did what she called "Beta testing" and created creatures called Jefferson Starships, which were hybrids that she mass produced. Her only known weakness was that of Phoenix ash. She was just recently killed by Dean who used its ashes on her.

Family Matters
She is first referenced by the Alpha Vampire, who is being interrogated by Samuel Campbell. When Dean and Sam have a few moments alone with him, Sam asks, "But if you're the first, who made you?" The Alpha Vampire answers, "Well, we all have our mothers. Even me."

Like A Virgin
Dragons are abducting young women (virgins) and keeping them captive in a sewer. Dean obtains the Sword of Brunswick and he and Sam track down the dragon's lair, finding a pile of gold watches, and the women. They also find an ancient manuscript which speaks of freeing Mother from Purgatory. Sam and Dean kill one of the Dragons but one escapes. He meets up with another dragon who has also captured a half dozen women. They take one and use an incantation to open a door to Purgatory. They throw the woman in, and she rises again giving form to Eve.

...And Then There Were None
Eve creates a being - called colloquially the Khan Worm - that can enter a person's body through the ear and control their actions. She plants it inside a trucker, who goes on to kill his family. It then passes to one of his co-workers who kills 12 people. While investigating the murders, it infects Dean who kills his cousin Gwen, and then infects Samuel who was killed by Sam, and finally Bobby who kills Rufus while possessed. While possessing Bobby, it tells Dean and Sam that it was created by Eve, who intends for supernatural beings to take over the world.

Mommy Dearest
Eve comes to town and begins experimenting on the citizens of that town. She is also able to neutralize Castiel's powers when he comes to town. When the boys finally come to meet her, they discover the diner she is located in, is filled with her creations. To further torment Sam and Dean, she turns into Mary Winchester. She tells Sam and Dean the reason why she is doing this, is because of what Crowley is doing to her children. Sam and Dean are surprised at this new information due to Castiel burning Crowley's bones earlier that year. She makes a deal for the boys: she tells them to bring her Crowley, so she can kill him for torturing her children, and she will let them live. Deans refuses and tells Eve to "bite [him]". Eve does and discovers that Dean had in fact drank some phoenix ashes, making his blood poisonous to her. Now with the ashes in her system, Eve dies.

Powers

 * Ash_of_the_Phoenix.pngImmortality: Eve is immortal due to having a agless lifespan, meaning that she is immune to aging and death through natural causes. She is not truly immortal as she can be killed by the ashes of the Phoenix.
 * Regeneration: Eve can heal from almost any injury inflicted on her, including injuries that would kill a normal human being. Her regeneration ability has limits as the ashes of the Phoenix negated her advanced healing powers.
 * Levitation: Eve can levitate herself telekinetically as she did when she rose out of Purgatory.
 * Possession: Eve can possess a human to use as a vessel similar to Demons and Angels. However, the vessel must a female virgin in order for her to walk the Earth.
 * Monster Creation: Eve has the unique ability to create a new breed of supernatural creature (or monsters) through two known means. The first is to touch a human, as her touch can transform a living being into a monster of her choosing. And she can give brith to a new species of supernatural creature as she did with the Khan Worm
 * Superhuman strength: Eve is physically stronger than humans and her children. Her strength is comparable to that of Demons and Angels, but she is likely weaker than Archangels as she used a spell to strip Castiel of his strength due to his status as a Archangel.
 * Super speed: Eve can move faster than the eye can see.
 * Shape shifting: Eve can shape-shift into any form she wishes much like Shifters, except her ability is more powerful. She changed into the form of the Winchester's mother with ease.
 * Invulnerabillity: Eve is imprevious to physical harm similar to that of Angels and possibly Archangels. The only known way to harm her is through the use of the ashes of the Phoenix.
 * Magical Knowledge: Eve possesses considerable magical knowledge due to her aqcuiring such knowledge over the centuries she has lived. She is able to render Castiel completely powerless through a spell she placed on herself. She also employed sigils that rendered her invisible to Castiel in much the same way that Sam and Dean are to Angels
 * Telepathy: Eve can telepathically communicate with other monsters, and can influence their behavior according to her wishes.
 * Superhuman senses: She managed to detect the Phoenix ashes within the guns the Winchesters brought with them with relative ease.

Trivia

 * A virgin is needed for sacrifice so as to release her from Purgatory.
 * She is played by Julia Maxwell.
 * She is the main antagonist of the second half of the sixth season.
 * It's possible that she is Echidna who, in Greek mythology, was known as "The Mother of All Monsters", however she calls herself Eve, who in the Old Testament of the Bible was the first woman to have been created, as well as the first woman to have disobeyed God. This does not count Lilith, supposedly a woman created alongside Adam who later left him and went on to have children with demons, because she is not universally accepted in Abrahamic religions.
 * There may be a distinct connection between Mother and the Winchester brothers. She calls herself Eve while Sam and Dean are blood descendants of Cain and Abel.
 * Confirmed fact: Eve is more then 10.000 years old.
 * Eve is even older than Castiel and other angels, as she knew how their powers worked and could negate them.
 * Despite taking a human vessel her true visage or a portion of it can be revealed on a camera recording.
 * Even after her death did her body still produced new monster eggs.
 * It looks like her latest offspring were linked to her,when crowley chopped into her dead brain so did the offspring fil the pain.

Appearances

 * Season 6
 * Like A Virgin
 * ...And Then There Were None
 * Mommy Dearest