Supernatural Season 7 Finale "Survival of the Fittest" Sneak Peek 2

Supernatural Season 7 Finale "Survival of the Fittest" Sneak Peek 2

What do nuns have to do with Sam and Dean defeating the Leviathans? Check out this sneak peek for tomorrow's Supernatural Season 7 Finale, Episode 23 "Survival of the Fittest," and find out.