It's the Great Pumpkin, Sam Winchester

It's a few days before Halloween and Sam and Dean investigate two mysterious deaths in a small town. The brothers find hex bags and deduce a witch is sacrificing people to summon a dangerous demon named Samhain. Castiel arrives in town and tells Sam and Dean the freeing of Samhain is one of the Seals that will lead to freeing Lucifer, so Castiel has brought a specialist angel named Uriel to smite the entire town.