There are only a few weeks left before the premiere of 'Supernatural' Season 11, and fans can finally see Sam Winchester (Jared Padalecki) team up once again with Mark of Cain-free Dean (Jensen Ackles) to take on the ancient evil simply known as The Darkness!

However, what exactly is the Darkness? And what happened to Castiel? And who else is coming back to 'Supernatural?' Executive producer Jeremy Carver recently spoke to TVLine to answer the important questions about the eleventh season. Just don't expect him to tell you more about the Darkness.

"I'd rather keep that cloudy, as it were, for now," Carver said, but he also added, "But folks will understand in the early moments of Season 11 exactly how The Darkness is going to manifest itself."

Jeremy Carver also confirmed that Castiel (Misha Collins) will still be under the attack dog spell when the eleventh season starts.

"Castiel, first and foremost, has to find a way out of this spell that Rowena has cast on him - and that's not as easy as it may sound," Carver revealed. "Being under the influence of this spell is going to lead him to some pretty uncomfortable situations."

As ominous as that sounds, Castiel fans can rest assured the angel will still be trying to help Sam and Dean Winchester.

"For Castiel, we're going to see him in something of a vulnerable state early on in the season," Carver continues. "He is working alongside the Winchesters while at the same time trying very hard to reestablish or redefine what his place in the universe is. He is, essentially, finding a way to get his mojo back."

The 'Supernatural' EP finally confirmed one of the rumors about Season 11 being filled with cameos.

"As responsible as the boys feel for having released The Darkness and how much they personally want to defeat it, they're not going to be able to do it alone," Carver said. "They're going to have to confront some figures from their past. They're going to have to make some unexpected and unholy alliances involving folks from their past, which will have personal ramifications, as well - because these are some pretty significant figures from their past."

'Supernatural' Season 11 returns to The CW on October 7.