The Supernatural Season 8 finale, Episode 23, "Sacrifice," airs tonight (Wednesday, May 15) from 9 to 10 p.m. on The CW.

Nothing major is at stake, just a plan to completely shut down Heaven, Hell and "all of it." No biggie. Here's the official synopsis:

"WHAT MUST SAM, DEAN AND CASTIEL SACRIFICE TO FOREVER SEAL HELL? - With Crowley (guest star Mark Sheppard) poised to undo all the good they've ever done as hunters, Sam (Jared Padalecki) and Dean (Jensen Ackles) find themselves cornered. But with Kevin's (guest star Osric Chau) help, the Winchester brothers bound into one last play against The Demon King. Metatron (guest star Curtis Armstrong) initiates a plan with Castiel (Misha Collins) to take on Naomi (guest star Amanda Tapping) and the bureaucracy of Heaven. Alaina Huffman (Abaddon) and Kim Rhodes (Sheriff Jody Mills) also guest star. Phil Sgriccia directed the episode written by Jeremy Carver."

Check out a preview of the finale here, and a sneak peek here.

Back in mid-April, executive producer Jeremy Carver teased the final Season 8 episodes to Entertainment Weekly, saying, “Inevitably, this is all leading to a big conclusion with Crowley. I think we’re going to see Crowley rising to a new level of ruthlessness we haven’t seen before in order to defend himself and his kingdom, as it were. I think we’re going to see Crowley presented with a new twist on things that will effect him forever, as well.”

Supernatural has already been renewed for Season 9, which will start this fall. Misha Collins will be back as Castiel, as a series regular. Read more Season 9 spoilers here.

 

Sources: Futon Critic, Yahoo, Entertainment Weekly