At a convention in 2016, Rob Benedict who played Chuck Shurley AKA God revealed there was an idea, the very early draft of Season 11 involved the demise of the lord. But the plan was scrapped. Season 11 saw the arrival of Amara, God’s sister who is the darkness and is needed for the existence of the universe. While God is responsible for the creation of nearly everything in the universe. But he didn’t create Death and Empty. Both of these entities existed before God. While Death is equal in terms of power to God. God doesn’t hold any power in the dimension of the Shadow. God has created the multiverses, all the alternate universes. Out of all, the main Universe with Sam and Dean is his favorite. He kept creating new worlds whenever he felt unsatisfied with his product. However, in Season 15 he starts eliminating the worlds one by one.
Amara AKA Darkness is the one behind the Mark of Cain, the mark was like a key which was used to trap the darkness and God handed it over to Lucifer. He passed it to Cain who passed it to Dean. The Mark of Cain corrupts its owner, it has the essence of the darkness in it which fuels the blade when the person wields it. The world Amara has its roots in the Sanskrit word ‘Amara’ which means to be immortal, to exist forever which perfectly sums up her character.
Eric Kripke recently revealed how much of a fan he is of Neil Geiman’s comic ‘The Sandman’ which at one point Kripke was planned to create within the bounds of a network television. He revealed that Sandman served major inspiration for the Supernatural, but other DC Comics such as the Constatine also played a part. The character of Darkness is comparable to the Great Darkness from the comics. The Great Darkness is the source of the darkness. In the comics, when the darkness is awakened and gains consciousness. Different factions of Supernatural heroes come together along with the celestial armies and demonic armies who join hands to stop the darkness. This is very similar to Season 11 plot arc where Chuck teams up with demons and angels.
Lilith is the first demon to be ever created in the SPN Universe. Did you know in the first two seasons Azazel served as the demon army commander with the goal of freeing Lucifer, he was a true devotee. However, after his demise, the writers had no clear to move forward with. According to the report, there was an idea to have demons act on their individual goals which we have seen in the beginning episodes of Season 3. However, they decided to introduce a new demon commander who turned out to be Lilith. They chose Lilith in the form of a little girl because it was simply terrifying. But had her possess an adult vessel so the Winchesters can harm her as any attack against a little girl would be..absurd.