The Winchester boys are trying to get the other two things needed to kill the Leviathans, but the Alpha Vampire is seemingly conspiring with the Leviathans.
Sam and Dean continue their mission to kill the Leviathans once and for all in the next episode of "Supernatural". In order to defeat Dick Roman (guest star James Patrick Stuart) and his crew, the boys must locate three key items, one of which has been found with the helps of Castiel.
The other two things are the blood of Crowley (guest star Mark Sheppard) and the Alpha Vampire (guest star Rick Worthy), which explains why two of the Winchester brothers' strongest opponents return in this episode. But they may not get the blood easily since it appears that the Alpha will double cross them by working with the Leviathans.
Bobby also returns in the penultimate episode of season 7, "There Will Be Blood", which is set to air Friday, May 11 at 9/8c. He tries out a new ghost trick that ends up being very dangerous. Castiel, meanwhile, is not featured in this outing, but he will show up once again in the season finale.
Misha Collins recently talked about what Sam and Dean will face in the season ender. "I guess the scope of the mission is more manageable [than in the past], but I think it's a tricky thing in this world because Supernatural has gone so big and as epic as the human mind can imagine," he said.
The Castiel depicter went on gushing, "But I think that what gives the show legs beyond those huge finales is that at it's core it's still a show about these two brothers and their personal relationship and it still is a character driven drama. It doesn't have to be about big, epic things in order to be riveting."
The CW has renewed the show for an eighth season.