I wonder what Dean would have done had Castiel not been waiting at the rift. Would he have stayed? He knows there's another way out--but it's only a door for Castiel if Dean can take him through it. On the other hand, he knows Sam's imperiled, didn't want to go to Purgatory in the first place. Even if he doesn't have the flower, maybe when it comes to Sam you just have to cut your losses and show up to take on God empty-handed.
Plus, it would be the cruelest kind of irony to realize you are choosing to stay in Purgatory instead of looking for your brother.
The prayer itself? I know a lot of people are either up in arms about or over the moon about its relevance to Destiel--which, obviously, I don't read it either of those ways. I know some people are angry about it, because they see it as invalidating Dean's emotions/needs and making him out to be/making him accept that he's the bad guy in the situation like he's some kind of out of control rageaholic. I don't read the scene that way, though it also doesn't surprise me that I wouldn't. Historically this kind of scenario is where I lose my Deangirl card. (Because even if something is invalidating Dean's emotional needs I'm typically very unbothered by it. So I can't really participate in that conversation in any real way. I'm not out to disprove any of that; I don't even think I think their analysis is wrong? I'm just starting from a different place and reading differently.)
I think there are two things here: Dean's rage being a thing that exists, and his apologizing for it. I think the angry people are right in that Dean actually has a lot of emotional awareness and emotional control, both of which he exercises successfully all the time. But I also believe that are very much scenarios where that's absolutely not the case, he is not in control, and he has no say over the intensity of his reactions or the depth to which those grudges/resentments/betrayals burn in. 100%. I mean, that's trauma. Those are triggers. I think what makes this so difficult for Dean to handle is exactly because he knows he's pretty self-aware and pretty self-controlled (when he commits to it). It's not a controlled fire; it's not even entirely his, or doesn't feel that way. It's outside of who he knows himself to be but is also deeply, intimately part of him now, and that makes it really, really hard. I think that's where his "I don't know what this is" comes from. He does, kinda. Trauma, depression, you know. The interaction and relation of the two. But what do those words mean, anyway? They're not helpful to him.
Whether Dean "needed" to apologize or not? I mean, I think Dean's reaction to Castiel in 15x02 far outstripped the logic of the situation, but like. Illogical doesn't mean the same thing as not understandable. Whether Castiel should have just understood and accepted or if he felt he shouldn't have to take this kind of shit anymore--that's up to Castiel. I don't think Dean "needed" to apologize to Castiel. The entire front end of S15 made pretty clear it was a strugglebus kind of time. I think at that point every exigency is just about staying on the strugglebus until you stop strugglebussing. But I think the person Dean wants to be would see the apology as requisite. That prayer was Dean trying to be that person. Which I guess it all of it, for me. Get after it, Dean. Go manifest. <3
I'm also curious about how Purgatory functions. It houses all the monsters that have ever died, but it seems like most of the time it's pretty quiet. It was riled up when Castiel first arrived in 7x23, because he was an Angel and an anomaly. A lot of the fighting we see Dean and Benny undertake, though, is in the context of interrogation. Not all of it--and I don't think Dean was exaggerating about "360 degree combat." But you don't have to be engaged in an actual fight to be in combat, to feel you are at war. It's mostly quiet when Sam visits, however briefly, though I'm sure opening gates to Hell and human souls floating around and Reapers pulling shenanigans probably upsets the balance.
I like to imagine that it's "rare" (more common than encountering them topside, but still) to meet a monster still wearing the corporeal form it entertained on Earth. It happens, of course, and some of them retain memories--often quite clear ones--of the time they'd spent there, similar to Ruby or Crowley in Hell. But you don't need to eat in Purgatory--there, Leviathan aren't defined by their teeth. The ones that are, you can kill with borax. But that is a rule from another world, and it only has its uses at thresholds, places where the fabrics of universes warp and weft, and monsters can codeswitch.
Most of the monsters in Purgatory are water. They are humus; moss; trees. They're the chill in the air (where do you think ghosts get it from?). The metal taint to the spring water, otherwise clear and fresh and untrammeled. They are the way it sits in your stomach, standoffishly mercurial. They're that dread.
That's why the Werther Box sends you there that one time--and you know it, don't you. You know what's why. The dread.
Eve is what comes after. Eve is the beginning--but there is no time in Purgatory, not really. There is no time, there are no beginnings, there is quiet and stillness and sometimes neither but there is no ending. Dread is fear of what comes next; but in Purgatory there is no next. It is the end but it's not one. (That's why you fight fire with fire--phoenix ash and Eve.) "Purity"--that's Eve, too. There are no beginnings there are no endings there is no Paradise no fall no postlapsarian time. To feel pure is to lose your relation to time, and your relation to fear and time. That's the hardest part about coming back to Earth. About learning how the world spent it without you--about how you will now have to learn to spend it, all over again. Re-learn fear, and dread.
That stopwatch on your phone? Time, in a place without it?
This time, you keep your fear with you.