When Dean woke the next morning, the sky was still dark. "Damn it, I forgot to ask Castiel what those last images were," he thought. He looked over at Sam. "I wonder what he makes of all this." He yawned and headed downstairs. Surprisingly, Bobby was already up and at the table piled with books. "You ready to do some more work on these texts?" Dean looked at the table and groaned internally. "Actually, about that, last night Sam was reading the Silmarillion. I'll let him explain when he comes back downstairs."
At that moment Sam walked in, looking extremely rumpled, like he had been tossing and turning the whole night. "Speak of the devil!" Sam grimaced automatically. "Sorry, I forgot. Anyway, you can explain that crazy theory you had last night to Bobby much better than I can." Sam took a deep breath and began explaining. "I was reading the Silmarillion that you gave me when I came across a certain passage..."
When Sam was done, Bobby had an extremely skeptical look, understandably. Before he could speak, Castiel appeared in the room. "I must tell you of an extremely urgent matter. Heaven is aware of your realization and will do anything in their considerable power to prevent you from reclaiming your past selves. The people you used to be were extremely strong willed, hardly conducive to their plans for you." Sam thought about this. "Maybe we can use this to our advantage. I agree to Lucifer after we get all four Horsemen's rings. Then you make a portal into the Cage where Lucifer is supposed to be, and Lucifer will no doubt want to remove the Michael Sword, you, from the picture. Before he does so, I gain control back and go through the portal."
He didn't say that he had gotten the idea from his memory of Maedhros leaping into the chasm.
As he expected, Dean and Bobby began protesting vociferously against his idea. "Are you nuts?" "That will mean you are stuck in the Cage too!" Castiel, though, was silent. "No. I released Lucifer and I will put him back in his Cage no matter the cost to me. I will do this no matter your objections." In that moment he greatly resembled Maedhros in spirit, the Maedhros who had stood against his father and brothers torching the Telerin ships, the Maedhros who had stood with Maglor alone against the host of the Valar in pursuit of his Oath, however regrettable.
The matter was thus decided. But Dean Swore to himself, silently, that he would get Sam out of the Cage, without Lucifer.
After the final ring was obtained from Death, a few days later, the mood at Bobby's house was extremely subdued. They all knew what had to be done. The four rings rested on the table, looking extremely small and harmless for objects that could open a portal to Hell. Bobby, Dean and Castiel would set them up. Sam knew that he would have to call Lucifer. No goodbyes were said. They would have been too small for all that was meant. He drove away.
In an abandoned building, Sam was ready. "Lucifer! I call you here. I say yes to you."