'Supernatural' Season 9, episode 22 recap: 'Stairway to Heaven' reunites Team Free Will for the finale
That's right, Castiel, Sam and Dean are all finally back together in one place, on the same side, with the same goal: To take down Metatron. After all of the angels following Castiel found out that he lied about his stolen grace -- he didn't tell them it was fading, and once it was gone it would burn him out as well -- they left his side to join Metatron, since he promised them all amnesty and a ticket to heaven if they called him "god." That was Metatron's goal from the start. He was posing as Castiel and convincing angels to "blow themselves up," and that combined with Castiel's lie turned all his troops against him. So Cas went back to the Men of Letters bunker with Sam and Dean, and now the three of them are the only ones standing against Metatron.
But is that enough? Castiel even wondered that out loud to Dean. "You really think we three will be enough?" he asked. "We always have been," Dean replied.
But wait! It's not just Team Free Will standing against Metatron, as his second in command Gadreel switched sides. After watching Metatron convince angels that Gadreel recruited to blow themselves up, he became disgusted with Metatron's actions. He made his way to the MoL bunker and promised Sam, Dean and Castiel that he would tell them all of Metatron's secrets and plans if they forgave him for his "mistakes" -- like killing Kevin Tran in the very spot they were all standing -- and things were tense for a moment. But then Dean stretched out his hand to shake Gadreel's in a sign of peace.
Honestly, that gesture was shocking and a little out-of-character for Dean. He's not the forgiving type (see: Reaper Tessa's murder earlier in the episode), especially since this is the angel that lied to him, stole his brother's body and killed Kevin. Dean's been clamoring for revenge against Gadreel this whole half of the season. So to see him be the first one to forgive and accept Gadreel's offer was strange.
And that's because it wasn't for real. Dean was only distracting Gadreel with a handshake while he snuck the First Blade out of his jacket pocket to attack Gadreel. He swiped at the angel's chest, cutting him pretty badly but not killing him. Sam and Cas leapt into action and restrained Dean before he could kill their one chance at finally beating Metatron.