Dean returns from Purgatory carrying Benny's soul in his arm and travels to Benny's grave in Louisiana. There, Dean performs a ritual, restoring Benny's soul to his body and resurrecting him.
Olsson first appeared on Supernatural in season 2 as a vampire named Eli but would later return to the show in season 8 as Benny, Dean's vampire bestie from his time in purgatory. He was last seen on the show in season 10.
In Purgatory, Dean, Benny and Castiel come under attack by monsters but kill them all. Both Benny and Castiel try to convince Dean to abandon the latter because as a Seraph, Castiel is drawing monsters to them. Benny tells Dean that the way out may not even work for Castiel as it is meant for humans only.
Castiel was later rescued by an incursion of angels sent by Naomi which she said cost many angels their lives. When Sam asks for entry into Hell, the rogue Reaper Ajay takes Sam to Purgatory where there is a backdoor into Hell.
Out of Purgatory. In "We Need To Talk About Kevin", Dean escapes Purgatory with the help of the vampire Benny, but Castiel is not with him. He later tells Sam that things got hairy near the end and that Castiel didn't make it, that he "let go". While Dean doesn't elaborate, he is clearly affected by this.
Benny Lafitte (Ty Olsson)
The Cajun vampire helped Dean escape Purgatory, forming an unlikely bond with the hunter. “Benny and Dean get each other,” says Olsson. “They both crave love, kids, friendship—things they can never truly have.”
Castiel secretly worked behind the Winchester's back. He raised Sam's body from the cage, but accidentally left the soul behind. He aided the Winchester into stopping Eve, though the Mother of All negated his angelic powers, rendering human for a while until she was killed by Dean.
Cassandra Masters is the daughter of Castiel and Meg Masters and the only known Nephalem to exist, which is a hybrid between a union of an angel and demon, even being part human due of Castiel and Meg's human vessels. Cassandra acts as one of the leading main characters with Sam and Dean.
The debates have been endless as to why Sam didn't look for Dean, but in this analysis, we have to go with what we're given - he didn't. Sam explains to Dean why, because everyone he knew was dead. There was no family left.
"What does this sound like a goodbye?" Dean asked. "Because it is," Castiel replied. "I love you." After admitting his feelings, Cas makes the ultimate sacrifice by letting the Empty take him away — along with Billie who had just arrived — after pushing Dean out of the way.
In the end, Dean (Jensen Ackles) went out the way he always thought he would: Hunting. He was killed in the series finale while taking on a nest of vampires, but his ultimate end would come in the show's final moments, when he was reunited with Sam (Jared Padalecki) in heaven.
With the help of Dean's vampiric friend Benny, Sam returns to Earth with Bobby's soul, but when Bobby goes to ascend to Heaven, he is trapped by Crowley, who wants to take him back to Hell to punish him for the "damage" he has done to demons in his hunting career.
Sam spends at least two days in Purgatory and Hell; it takes Sam 7 hours to and 7 hours from the back door into Hell from the spot he arrived in at Purgatory, as Ajay tells Crowley he will be retrieving Sam in 17 hours when Sam arrives at the entrance to Hell.
Dean's plan is to kill Benny so that he can return to Purgatory and lead Sam and Bobby out the same way he took Dean with Benny returning with Sam this time. Benny agrees, saying he no longer feels like he fits in on Earth. After saying their goodbyes, Dean decapitates Benny.
He became the meat suit for the Archangel Michael…with a twist, of course. It's not the Michael that wanted to go head-to-head with his brother, Lucifer, all those years ago. No, this is the Michael from the apocalypse world. The one who tortured our Lucifer and made his life hell on Alt!
Boris later sees Dean in an alley and, after telling him he's pretty, he attacks and feeds him his blood, turning Dean into a vampire.
A short time later, Dean remained suspicious of Sam letting him be turned into a vampire. After Veritas revealed that Sam was lying, even under her power, Sam admitted that he let Dean get turned into a vampire as he knew about the cure and that they could turn Dean back.
Before dying, John tells Dean, if he can't save Sam, he'll have to kill him, should he become evil. The fourth season episode "On the Head of a Pin" reveals that the demon Alastair tortured John in Hell for over a century, with John refusing the demon's offer to stop if he himself would torture someone else.
After Dean died in the series finale, Sam went on to get married and have a child, whom he named after his brother.
When telling Sam to go after Dean and Castiel, she refers to Castiel as "my unicorn" which is what she had called Amelia Richardson after learning that Sam had stopped being a hunter because of her. Meg ultimately sacrifices herself to hold Crowley off to buy Sam, Dean, and Castiel the time they need to get away.
Castiel tells her that within Crowley's fortress she can't escape due to a spell. Out of options, Meg decides to stay back to fight in order to give Sam and Dean a shot at killing Crowley. In order to get a weapon, Meg kisses Castiel, taking his sword.
This is likely a reference to the musicians Richard Tandy and Jeff Lynne, both members of the rock group Electric Light Orchestra. Meg calls Castiel "Clarence." Clarence is the angel trying to get his wings in It's a Wonderful Life (1946).
Cass reveals that he has learned a lot about being human and reveals he had sex with April, leading the Winchester's to be surprised. Dean even goes onto make a joke about "having protection." Castiel goes to eat and Ezekiel takes over Sam saying Cass can't stay because he will bring the angels down on them.
However, his affection for Castiel ultimately won, with Dean shown in tears in Purgatory when he thought he'd lost Castiel. Their reunion was their most intimate yet, as the two didn't hold back on letting the other know that they were truly sorry and didn't want to fight anymore.
At the same time, some fans were perturbed that Dean did not reciprocate the feelings, as this implied Castiel's love had been unrequited for all these years. Many were also upset that following the declaration, Castiel was pulled into the Empty which is where angels go when they die.