Sam Winchester visited Lucifer in Detroit and said "Yes" to possession. Lucifer abandoned his former vessel and used Sam to win the war between Heaven and Hell and bring about the end of humanity. He led the demons in a successful war and with the release of the Croatoan Virus, the human population was greatly reduced.
Either by the powers of Cambion Jesse Turner or by their own choice, Heaven left the Earth, allowing Lucifer free rein over the state of the Earth. The remaining survivors formed a group known as Camp Chitaqua.
|“||I know you won't. I know you won't say yes to Michael, either. And I know you won't kill Sam. Whatever you do, you will always end up here. Whatever choices you make, whatever details you alter, we will always end up—here. I win. So, I win.||”|
in The End
Dean meets the members of Camp Chitaqua who are led by his counterpart, the Dean of 2014. Having recently obtained The Colt, 2014!Dean intend to face off against Lucifer in what is akin to a suicide mission. He allows Past!Dean to tag along while the remaining members of the Camp at as a decoy.
The group arrive in Detroit and 2014!Dean confronts Lucifer. He is however, easily overpowered. By the time Past!Dean reaches their location, Lucifer is posed to snap 2014!Dean's neck, which he does. Turning around, he is genuinely surprised to see the other Dean, but greets him with a smile.
Lucifer tries to convince Past!Dean that he does not wish to destroy the world, only purify it. He describes the Earth as God's last masterpiece. He insists that he was unfairly cast out and wishes for Dean to understand his plight.
Dean is not fazed by his words and simply compares Lucifer to a cockroach with a big ego. Lucifer simply smiles and comments on how he likes Dean. He insists however, that things will turn out as planned and Dean will not say "Yes" to Michael, and Dean will always end up right here in Detroit, no matter what.
Soon after, Past!Dean is taken back to his own time by Zachariah.
This Lucifer shares his counterpart's unrelenting hatred towards humanity and his sense of betrayal and unfair treatment at the hands of his father. He shows no remorse in the destruction he has caused, and seems to view it as a necessity.
Unlike his counterpart however, this Lucifer professes love for the planet Earth, praising it for its beauty and finding the idea of him causing damage to it as rather humorous.
Similar to his counterpart, this Lucifer also believes fate will drive Sam and Dean to play their parts. While he is right that Dean never says "Yes" to Michael and Sam does say "Yes" to him, the brothers have planned out a way to re-imprison Lucifer by sacrificing Sam and allowing Sam to jump into The Cage.