"Supernatural" season 10 spoilers reveal that Dean's past will finally catch up to him with Cole's appearance, as Castiel prepaers for doom.

Samantha Highfill wrote "Supernatural" season 10 spoilers on Entertainment Weekly as she revealed the appearance of a new character named Cole.

"It gets very interesting in that Sam is hunting down his brother, who he eventually will discover is a demon-he doesn't know that on the onset-and with the hopes of saving him or curing him in some way," showrunner Jeremy Carver told EW. "While you've [also] got this character of Cole, who is hunting down Dean for entirely different reasons.

"It's going to cause all kinds of complications, and the character of Cole is someone who will evolve from how we see him to something very different once he finally does come face-to-face with Dean," he said.

Misha Collins, meanwhile, revealed "Supernatural" season 10 spoilers when he said that Castiel is already preparing for his death.

"Cas has developed a somewhat fatalistic perspective on life - he feels like he's doomed. The only solutions he has are to get Metatron's co-operation, which he's too prideful to do, or to slit an angel's throat and steal its grace, and he doesn't want to kill any more angels. So he's somewhat resigned to his own expiration," he said.

But he said that Castiel and Sam will continue to bicker. "Castiel wants to get the old Dean back, but he's also determined to get rid of demon Dean, whatever that takes. If that means there's no choice but to kill Dean, Castiel is willing to go there.

Earlier, Jensen Ackles revealed "Supernatural" season 10 spoilers to TVGuide during the San Diego Comic-Con panel. He said that Demon Dean will be very different because he's tainted with the Mark of Cain. "This is Dean's soul, but it's twisted."

He revealed that in the first few episodes alone, Demon Dean mauled three guys and killed two people.