The two-hour back-to-back finale of "Supernatural" season 12 showed the Winchester brothers' fight against the British Men of Letters and Lucifer. The finale was heart-pumping from start to finish, and the ending teases that there is more to expect in the upcoming season.

Amid all the action and suspense, the finale was also a truly emotional one. Dean and Sam got back the mother that they know from their childhood after being brainwashed by the Brits. Meanwhile, a character that has been in the series for so long had to say goodbye. If you have not watched "Supernatural" season 12 finale yet, please be warned that there are heavy spoilers below.

The Winchesters are suffocating to death

The first part of the finale is an episode titled "Who We Are," showed Dean, Sam, and Lady Toni Bevell, after almost suffocating to death, were finally able to get out of the bunker using the grenade launcher. Mary, on the other hand, is brainwashed and is on a killing spree, hunting Hunters, and she is after Jody Mills. But with the help of Alex, Jody was able to knock her out and restrain her.

The Winchesters rallied the remaining Hunters to fight back against the Brits. Toni placed Dean in a trance so she can get inside Mary's head. However, as Mary was about to acknowledge Sam, Mr. Ketch woke him up and kills Toni. The now un-brainwashed Mary shoots Ketch in the head.

The first half of "Supernatural" season 12 finale ended with the killing of the Brit's general, and the revelation that Lucifer is back.

'All Along the Watchtower'

The second half showed Kelly finally going into labor. Castiel found a crack in space and time, or an alternate reality, where everything that Sam and Dean know do not exist.

Lucifer shows up to meet his son, while Sam, Dean, and Castiel try to lure him into the alternate world. Lucifer followed, and Dean fired his machine gun.

Crowley said that the would seal the gates of hell, and to do that, he crafted a potion, but it asked a life to complete it - and so he gave up his own. But Crowley gave up his life for nothing because Lucifer was able to return to the real world.

Dean and Sam were able to make it back home, but Lucifer stabbed Castiel, and it looks like he won't be able to make it. This is where "Supernatural" season 13 is going to pick up, hopefully.

Fans have a lot of unanswered questions, but we will have to wait until the next season for some answers. "Supernatural" season 13 is expected to premiere this fall. Preparation will start next month, and filming will begin in July.