This story is a sequel to Supernatural Ponies 1: Welcome to Equestria: Here's a Case

Following the events of Supernatural Ponies 1, Sam, Dean, Bobby, Castiel, and the Mane 6 must find a way into Hell in order to stop Crowley. Twilight figures out what they must do and they travel to YakYakistan. From here, all the ponies embark on their journey to Hell.

Sam and Dean Winchester, along with Bobby Singer and the angel, Castiel escape into a tunnel that transfers them to the world of Equestria. Things are odd at first. Everyone is so different from what they're used to.
Once they start to fit in, even Derpy Hooves would be able to see that something sinister was happening. The four newcomers to Equestria and the mane six are summoned by Celestia and Luna. They hire all 10 of them to hunt down whatever is raising hell in the world of ponies.
The mane 6 soon find out, the 4 ponies who just came into their lives are not what they seem. And the world of Equestria has many dark entities that are now rearing their heads more often.

Supernatural Ponies will be a trilogy.