WARNING: If you don't want to know what happened in this episode, don't read this photo recap!
The team is still trying to bring magic back to the world, and they've collected the seven keys to do so. They know that they have to find a "Castle at the End of the World" and they need to get there quickly, because the people who work in the library want to control magic by syphoning it off.
Julia, meanwhile, has been reached by a messenger god named Iris, who arrives to tell her that she's a full-on goddess now. Turns out, Our Lady Underground gave Julia that magic seed, and now she is "Our Lady of the Trees." She gives Quentin enough magic for one spell, says her goodbyes, and off she goes to fulfill her destiny.
The team realizes that someone must have built the Castle at the End of the World and figure out that it was Calypso: an architect who built the castle as a prison to trap a great power. There is a knight there to protect it, but it's powerful. So powerful that Prometheus gave up his power to protect it.
The warning, though, is very clear. They'll get in and figure out what they need - but what's locked inside that castle can never ever be allowed to escape. (We've heard this before, in an alternate timeline, right?)
Quentin tells the gang that he's going to stay behind in the castle and take over Ora's position. Margo and Eliot suggest that they take the god-killing bullet with them, but Quentin is adamant. He's going to sacrifice himself for the team, so they can all save magic together and protect whatever's in that castle from escaping.
Meanwhile, back in Fillory, the Fairy Queen tells Fen that someone is hunting her people. Fen sets a trap and discovers it's, yes, Irene McAllister. Now it's the Queen's turn to offer herself for a sacrifice. In exchange for fairies always being safe from harm, the Queen offers herself up to the McAllisters to make into magic cocaine. Who accept the deal.
Meanwhile, Alice goes to Dean Fogg. She needs a potion that will make her forget all magic and assume a different life forever. From there, she finally tells Quentin she loves him and that she'll miss him, even though she won't remember him. Oh! Also! It turns out, Dean Fogg is in cahoots with the Head Librarian.
The gang reaches Castle Blackspire and it turns out that everyone has different plans. Alice sneaks off, and Eliot and Margo exchange glances as Quentin meets with the monster. That monster turns out to be a youngish boy who is all-powerful and simply WANTS. Even the Gods can't stop him. But...
Eliot has brought that god-kiling bullet and shot the kid. Eliot didn't want Quentin locked in a prison for the rest of his life. Which is a dreadful mistake, as it turns out. And then…Alice also decides to take matters into her own hands.
As Eliot and Margo bring Alice back to the throne room to fix the key problem, Julia appears. She uses her god-magic to recreate the keys. Because of Quentin's willingness to sacrifice himself for the team, she is sacrificing her god-powers to recreate the keys. Just like Prometheus did.
Not so fast. Irene McAllister, that representative of the Library, and Dean Fogg turn up and place the syphon on top of the fountain. Effectively putting the Library in charge of all magic again. The quest actually failed.
Dean Fogg gets to re-open Brakebills, but magic is spotty, so he now has to request magic current from the Head Librarian, who, by the way, has Alice trapped there for breaking her deal with the Library. It seems everyone else though, is off doing things...