|“||I got something you need. (...) A way out. (...) There is if you're human. God has made it so. At least, that's the rumor. (...) It's a human portal, jackass. Only humans can pass through. I show you the door, you hump my soul to the other side.||”|
|“|| Castiel: The risk of crossing Purgatory with a seraph - it's... less than strategic, and certainly when we have no reason to believe that I can pass through the door that you're headed for.
Benny: You see, you're an intact, living human being stuck in Purgatory's craw. This dimension wants to spit you out, which is exactly what's gonna power our escape pod. Now, I'm pretty sure I can squeeze through, too, because, after all, you take away the fangs and the fun, I was born human, too. But...
After meeting Dean when he is trapped in Purgatory, the vampire Benny Lafitte tells Dean about the portal and offers to lead Dean to it if he will give Benny a ride out as the portal is for humans only. With no better options, Dean reluctantly agrees, but insists on finding Castiel first.
After finding Castiel, Dean tells Castiel that they are getting out despite Castiel's demands for Dean to leave him behind as he is being hunted by Leviathans. Benny warns that while the portal exists, he has no idea if its "angel friendly," but Dean continues to insist and Castiel finally agrees.
As the trio makes their way through Purgatory, they argue about the idea of attempting to use the portal with Castiel. Benny and Castiel point out that the portal is meant for humans only and Benny may be able to make it as a former human, but they express doubt about Castiel's ability to use it as an angel. Despite their arguments, Dean refuses to leave Castiel behind and continues to insist on them trying to get out together no matter what.
As the group nears the portal's location, it opens in response to Dean's presence. Having grown to trust Benny completely, Dean stores the vampire's soul in his arm and makes his way towards the portal with Castiel. However, before they can reach it, they are attacked by two Leviathans. The hunter and the angel quickly dispatch the monsters and Dean enters the portal as its beginning to close. Dean attempt to pull Castiel up onto the ridge with him, but Castiel lets go of Dean's hand on purpose and is left behind as the portal closes and sucks Dean along with it.
After a year spent in Purgatory, Dean emerges from the portal in the 100-Mile Wilderness in Maine. Dean subsequently makes his way Louisiana where he keeps his deal with Benny by resurrecting the vampire with a ritual. Though Dean is back on Earth, his failure to save Castiel continues to haunt him and he comes to believe that he failed to get Castiel into the portal instead of remembering that Castiel purposefully stayed.
Following Castiel's rescue by angels under the command of Naomi, Dean becomes suspicious, especially since making it to the portal almost killed him. Subsequently, Castiel shows Dean what truly happened at the portal when he realizes that Dean doesn't remember the truth.
During the Rescue of Bobby Singer, Sam becomes trapped in Purgatory when Crowley kills the rogue Reaper Ajay, Sam's only way back. In order to rescue his brother, Dean requests that Benny allow Dean to kill him so that he can return to Purgatory and lead Sam out through the portal as he did for Dean with Sam carrying Benny out as Dean did. Benny agrees as he no longer fits in on Earth and upon finding Sam and Bobby Singer, leads them to the portal.
At the portal, Sam stores Bobby's soul in his arm as Dean did with Benny, but Benny has no intention of leaving and they are interrupted by hostile vampires. On Benny's order, Sam enters the portal, but leaves behind his Purgatory Blade for Benny to fight. As the portal closes and takes Sam with it, he watches Benny fighting the vampires to buy him the time he needs. The portal returns Sam to Earth in the 100-Mile Wilderness as it did with Dean where Dean is waiting for him.
Situated on a ridge in Purgatory, the portal opens automatically when it senses humans nearby. Due to its design by God, the portal is only able to carry humans through it, but a human can store a soul in their arm for the journey through the portal and the soul will be allowed to pass. It is suggested that this is because many monster species were originally human so they are still human enough to pass in that way. It is unknown if an angel could pass through the portal, but it is believed not.
In order to use the portal, the user must simply step into it. As long as the user keeps one foot outside of the portal, they will not be immediately transported. If the user is still standing inside the portal, they will automatically be sent back to Earth as it closes. It is unknown if the user can return to Earth by walking all the way inside or must wait until it closes with them in the doorway for it to work.
On Earth, the portal opens in the 100-Mile Wilderness in Maine and deposits the traveler in a flash of light, the only indication of its usage.