Better turn on your lights because rumor has it the Season 10 finale of “Supernatural” is going to be dark -- really dark. And luckily for fans, Jeremy Carver, the executive producer of the hit CW series, teased just was kind of darkness will lurk throughout the chilling episode “Brother’s Keeper.”

During an interview with TVLine, the showrunner revealed that the sinister character Death (Julian Richings) will play a pivotal role in Wednesday’s episode, which is set to air May 20. But, of course, The Grim Reaper’s presence is “not a good thing. Ever,” Carver divulged.

Although The Horseman is the only one who can cure Dean (Jensen Ackles) from the menacing Mark of Cain, Death’s part in saving the life of Sam’s (Jared Padalecki) brother will come at a cost. And a hefty one at that.

Carver revealed Death will remove the mark at “a fairly sizable, non-negotiable condition.” But as risky as that sounds, Sam won’t bat an eye at making a deal with the devil himself in order to save his older brother. “I don’t think we’ve ever seen him go further,” the EP confirmed, saying that Sam will go to the ends of the earth in order to keep Dean alive.

Ackles previously teased during an interview with Variety just how determined Sam is to find an antidote for his brother -- even if it results in his own death.

“Sam can’t find a cure, and of course, the loyal brother that Sam is will die trying, and Dean knows this,” the actor revealed, teasing “Supernatural” may have another casualty up it’s sleeve.

The long-running series is no stranger to giving fan favorites the ax. Just recently Charlie (Felicia Day) was killed off in bloody ending during episode 21 after she endured multiple stab wounds.

“My goodness, it was wrenching for all of us!” Carver dished to TVLine just how hard it was to say goodbye to the beloved hacker. “It always is when you’re letting go of a beloved character, whether it be Charlie or Bobby (Jim Beaver) or Kevin (Osric Chau), and even worse when you’re saying goodbye to as wonderful a human as Felicia Day.”

Hopefully fans won’t have to bid farewell to any more characters during Season 10. But then again, this is “Supernatural” we’re talking about. There are always high risks -- especially when it involves the Winchester brothers. The finale synopsis reveals a "shocking decision regarding the Mark of Cain" will be made that will alter both Dean and Sam's lives.

What do you think will happen in the Season 10 finale of “Supernatural”? Sound off in the comment section below with your predictions before episode 23 airs Wednesday, May 20, at 9 p.m. EDT on the CW.