There’s only one all-powerful God. On Supernatural, though, there’s one being who’s even more powerful than him: the Darkness, God’s older sister.

The Darkness was the big bad of Supernatural’s eleventh season and will return for the series’ fifteenth and final season. Before she reappears, however, CBR is here to fill you in on who the Darkness is, how she returned to Earth and her relationships with God and Dean.

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Who Is the Darkness?

The Darkness is a primordial being who predates Death and even God. Death describes her as, “a horribly destructive, amoral force.” Meanwhile, God calls her “nothingness.”

Before the universe existed, God and the Darkness were alone together. But then God started to try his hand at creation and the Darkness became jealous. She destroyed every world he built, believing he shouldn’t need anything but her.

So God created the archangels, the first sentient life. God and the archangels waged a war against the Darkness. They eventually beat her. Instead of killing her, though, God imprisoned her with what came to be known as the Mark of Cain. The Mark served as both a lock and key for her prison.

God entrusted the Mark to Lucifer, but the Mark turned out to be a curse. It corrupted Lucifer, leading him to become jealous of humans. When he refused to bow down to them, God sent Lucifer to Hell. Later, Lucifer passed the Mark to Cain. Millennia later, Cain passed the Mark to Dean Winchester.

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How did the Darkness Come to Earth?

When Dean acquired the Mark it began to exert its corrupting influence on him. Dean went to Death to ask him to remove it, but Death refused. He explained that in order to keep the Darkness locked away, the Mark can never be removed, it can only be passed along to another person.

However, Sam had already enlisted the powerful witch Rowena to perform a spell to remove the Mark. The spell worked and shortly after the Mark was erased from Dean’s arm, a huge, dark cloud — the true form of the Darkness— touched down on Earth. Although the Darkness spared the lives of Sam and Dean, everyone else who came in contact with her smoke became infected with a disease that turned them dangerously aggressive. After a certain amount of time, the infection eventually became fatal.

During the chaos following the Darkness’ release, Dean and Sheriff’s Deputy Jenna Nickerson took a newborn baby named Amara from her infected father. They brought the baby to the safety of Jenna’s grandmother’s house, only to discover that the Darkness had taken the baby as a vessel -- and Amara had the Mark of Cain on her left shoulder. As a result, the Darkness also became known as Amara.

At Jenna’s grandmother’s house, it became clear that Amara possessed supernatural powers. She could move things telekinetically and she fed on people’s souls. Each time Amara ate a soul, whether human or demon, she grew older and more powerful. As a result of her boundless appetite for souls, she grew quickly from a baby into a teenager. During that time, she was under the protection of the king of Hell, Crowley, who was hoping to gain her loyalty.

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What Does the Darkness Want?

The Darkness’ goal is simple: She wants revenge on her brother for imprisoning her and leaving her isolated and alone for eons. Once she grows into an adult and has her full range of powers, she begins to work to settle what she calls “the oldest grudge.” However, Amara soon ran into a problem when she was unable to find God because he went into hiding. Her attempts to lure him God out of hiding through attempts to get his attention, including her torture of Lucifer, God's supposed favorite son, ultimately failed, as well. Eventually, Metatron convinced God to intervene on his creation’s behalf.

During her search for God, it became clear that Amara wasn’t affected by angel sigils or supernatural warding. Even a smiting from every angel in heaven weakened her but didn’t bring her down. So ultimately the forces of heaven and hell come together to take a stand against Amara. First, Rowena and a group of other witches combined powers to weaken her. Then, the angels in Heaven wounded her by smiting her again. Next, the demons, including Crowley, attacked her. It’s at this point that Amara found her brother waiting for her. While she’s distracted by the sight of him, Lucifer attacked her with his spear. Battered and bruised, Amara tells God he’s won, assuming he'll kill her.

When he starts to make preparations to imprison her once more, though, she attacks God. Amara is unwilling to be locked away again, and her desire to avoid that fate gives her the strength to fight back. She leaves God dying so he can see the obliteration of everything he built before passing away.

Connection With Dean

While Amara wasn’t a fan of her brother’s creation, she did have an affinity for Dean. She viewed Dean as the person who released her from her prison. As a result, she believed they were bound and would always help one another. Amara put her words into actions by saving Dean’s life more than once.

Amara even asked Dean to become a part of her. While Dean and Amara both admitted to being attracted to one another, Dean refused Amara’s offer.

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Why the Darkness Left and How She Could Come Back

God and The Darkness mock Sam and Dean in Supernatural

In a last-ditch effort to save Earth, Dean armed himself with a weapon made of thousands of souls that was supposedly powerful enough to destroy Amara. Before detonating it, though, Dean spoke to Amara about the futility of revenge and the unconditional love of family. With that, Amara brought God to her, healed him, and told him that she now saw that what he created was beautiful. The two forgave one another. Then, after God relieved Dean of the soul bomb, the pair left Earth to spend some quality time together.

While God always seemed to be on Sam and Dean’s side, after they betrayed him at the end of the fourteenth season, God turned on them. With God now taking on Sam and Dean, it seems Amara will also get into the mix. Emily Swallow, who plays Amara, tweeted on the subject, writing, “It’s high time for Amara to step in and set little pipsqueak brother Chuck [aka God] straight.” It’s likely that Amara still feels a connection to Dean. That could be enough for her to square off against her brother for Sam and Dean's sake. Amara could be just the ally the Winchesters need in their conflict with God.

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Returning Thursday, October 10 at 8 p.m. ET/PT on The CW for its final season, Supernatural stars Jensen Ackles, Jared Padalecki, Misha Collins and Alexander Calvert.