It is a shaken and exhilarated Lily who appears before him a year later, materializing from the shadows like any of the lesser gods of his realm.
She pounces on him, dragging him off to their bed, and only half-explains her state between kisses, far more interested in fucking him senseless than telling him what has happened.
He indulges her. He never could say 'no' to her, even when he wanted to, and he most certainly doesn't want to in that moment. There will be time enough for explanations later.
It is nothing like their first (and only other) time together. That was exceedingly awkward. He had been a virgin and unready, and she so very young: both of them innocent, for all they thought themselves wise in the ways of magic and the world.
Now they have seen war, seen the heights and depths of which the human soul is capable. They know not only magic and the world, but their place in it. (Together, always.) This is poetry embodied: the coming-together of two halves too long divided.
They lie together after, sated. Severus feels as though his life – or his afterlife, perhaps – is now complete. Lily looks at him and gives him a rueful smile.
"I shouldn't have done that," she admits.
"Do you regret it?" He knows she doesn't.
"No. But I'm married now, you know."
Severus sneers. "Potter is less than nothing compared to you and I."
She laughs, for they both know it is true. Here they are timeless and eternal, power incarnate. Potter is, will be, simply another dreamer in the Fields of Asphodel when he finally arrives. "I did it, Sev," she grins.
"Did what?" He still does not understand the disjointed explanation he was only half-listening to as she seduced him.
"Remember when I first came here? I could visit the mortals who called for me, but I could do nothing in their world but speak to them. But today… I called the Dead, and they obeyed me as though I were standing on the banks of the Styx. They rose up and they killed for me, when I ordered them. It was glorious, Sev. For this one minute, I could feel it all coming together!"
He knows the battle she is talking about – it is the one where he once felt relief to see some evidence that she was not entirely lost to the Light (a fear which, in retrospect, seems rather ridiculous: the Queen of Death, a Light witch? Never). He is at a loss to answer, though he is overjoyed at the thought that she is coming into her own as a goddess in truth, wielding the power of their realm even on the mortal plane. He simply kisses her again, and she responds as though she will devour him, beginning with his mouth.
When she is finally exhausted, he watches her sleep for some time, thinking on her appearances in his world. He suspects that their time together has already happened in the life he once lived and she is still living, like a time-loop. Knowing what he knows now of the circumstances of the Diagon Alley Massacre, it is clear: they can do nothing that will break the continuity of history. She is nineteen, now, and she must return to the land of the living. There are still two more years before he can claim her as his own, for eternity.
The longer he keeps her here, the longer that time will be in coming. He is fairly certain that even now, she can only come to him on Samhain, when the Veil between their worlds is thin. To allow her to tarry when she comes is only to delay the day when she finally will not have to leave him again.
Perhaps it is selfish, for the year will pass much more quickly for him than for her, but he paints her lips with the fifth drop of blood (He watches, fascinated, as her tongue ghosts over them in her sleep.) and sends her back to the land of the living.