Dean and Cas separated, Dean's entire face beat red and Castiel's wings, hidden from view on another plane, fluttered with giddy joy. Finally, after what had felt like an eternity, Dean Winchester and Castiel kissed at last. Dean felt like his chest was about to burst, he was so unimaginably excited. In all the millions of years Castiel had lived through, he was beyond positive that this was by far the greatest moment of his entire existence. For once, Castiel the fallen angel was truly happy.
There are little to no ways to describe the sensation of absolute disappointment and horror that Castiel felt in the next few seconds. It was like his heart had been put through a vice, blender, and meat grinder all at once as the space above and behind Dean caved in on itself. A huge black expanse opened up, spilling dark ooze onto the ground like a gaping, drooling mouth of a predator. Dean noticed the change in Castiel's expression right away, but didn't react in time as the jet-black figure covered in the dark slime reached out and grasped Castiel's wrist and darted back into the dark void. Castiel grabbed Dean's shoulder, and Dean put both hands on Castiel's arm and leaned back. "Cas! What- hold on!"
The Empty pulled with immense strength on Castiel's other arm, but Dean would not give up so easily. Cas was still having a hard time grasping what was happening. The truth was just to awful to face. But deep down he knew that there was no way to fight it, no possible escape. "Dean," Castiel started to say calmly, tears pooling in his deep blue eyes. Dean shook his head, tightening his hold on the angel as Castiel's started to loosen. "Don't you fucking dare!" Dean ordered, his voice unsteady. "Dean," Castiel said again. "It's okay. Let go, Dean."
"No, no you can't do this!" Dean insisted. "Not now! Not ever!"
Castiel smiled, and one of his tears landed on Dean's cheek. "There's no cheating Death. Not this time. I'm sorry Dean, but I have to leave. Thank you for making these last years of my life the best ever. I, I love Dean."
Dean gritted his teeth as he dug his heels into the soft dirt, although his efforts were in vain. "No, no. I won't let you." Dean said hoarsely.
In one last surge of strength, Castiel pulled himself forward and placed a kiss on Dean's forehead. "Take care, my righteous man," he whispered.
And then, he was gone. Dean was left alone on the field alone. He fell to his knees, his eyes wide and crying oceans. Dean held his head in his hands, and begged God to do this one last thing for him because a life without his love, especially now, was not going to be possible. But alone the hunter remained, jeans stained with mud and heart falling into the depths of nothingness, like where Cas must have been at the time. Dean could still Castiel's lips upon his forehead, a memory already begging to become distant. Cold ice began to encase his heart, and that was the last anyone heard of Dean Winchester.