TVLine and EW have posted their Season Finale Previews for several shows.

PRE-FINALE: As the British Men of Letters start to make their move, “people that Sam and Dean know/love pay the price,” forcing the brothers to take “a much stronger role in the wider hunter community” as generals, executive producer Andrew Dabb previews. Mary also faces a difficult battle with the Brits: She, “more than Sam and Dean, is on the inside, so her journey out may be a little bit more complicated,” Dabb notes. Meanwhile, Cas’ return brings “a lot of clarity” about “why he’s been in Heaven for so long” and “his own point of view on why he went.” And as the impending birth of Lucifer’s Nephilim offspring nears, “everyone is going to activate more and more.” Also on tap: the returns of Jody Mills and her surrogate daughter Alex, and “two surprise appearances, one by a relative newcomer and one by an old favorite.”

SEASON FINALE (MAY 18): The two-hour finale – the first episode deals with the Brits, while the second is Lucifer-centric – is “big and, I hope, somewhat bold and, in some ways, heartbreaking,” Dabb shares. The closer “also opens up some new stories for Season 13 in a very interesting way.”

See all of their predictions here.
From EW.

The CW, Thursday, May 18, 8 p.m.

The long-running drama has explored just about every option when it comes to season-ending suspense for its characters. Facing the apocalypse? Done. Being dragged to hell? Check. Killing death itself? Yep. (Try to wrap your head around that one.) But the season 12 capper will find Sam (Jared Padalecki) and Dean (Jensen Ackles) surrounded by enemies — and, thankfully, a few friends — as they deal with Lucifer and the British Men of Letters. "We’re going for a more traditional Supernatural season finale, where people will die, people will live, and people will be in danger," showrunner Andrew Dabb says. "[The episode] leaves everyone in an extremely precarious position. We are very conscious about this whole idea of opening new worlds."

Two surprise guests, who do you think they are? Sam and Dean become generals in the battl with the BMOL. Will Mary work as a double agent? How will the battle with the BMOL end? Why was Cas in Heaven so long? What big, bold, heartbreaking thing will happen? Let us know in the comments or in the discussion thread Season 12 spoilers and episodes 22 and  23.