Rhaegar trudges up the stairwell, half-mad with grief and filled with rage. In his wake the bodies of enemies lie still and unbreathing. ("You took her from me. You took her and killed her!" Oberyn Martell yells. "And I've taken yours in return. It's only fair, good-brother.") It's too late, he knows, but still a small part of him dares to hope that all isn't lost.
Only, of course, that all is lost. Oberyn is many things, but a liar isn't one of them. ("I've taken yours in return.") Lyanna has been dealt with in precisely the same manner Elia had. Rhaegar struggles to keep the contents of his stomach from spilling out at the sight of her. ("The Mountain stabbed the little Princess over and over and bashed the baby's skull in. Princess Elia, he defiled her." Jon Connington is silent after that for a long time.) Shaking hands touch the once white flesh. Stained red, lacerations open and sour, she looks nothing like the woman he left behind.
"I'm sorry, I'm sorry," he tells her, taking her stiff hand in his. She's cold. As if his regret can breath life back into her. As if mere words can bring back the second son he's lost. Elia had been ash by the time he got to King's Landing. His words had meant nothing to her too. "Lyanna, I'm sorry, my love." He bends his head down, willing the nightmare away, willing her to open her eyes. "Lyanna, please!"
("That little bitch of yours couldn't even fight by the end. I did her a kindness by slashing her throat. It's more than your knights did for my sister," Oberyn spits.) For Oberyn it's always been about Elia. He raises Lyanna's head gently, mindful of the wound splitting her neck open. Without the scent of decay and the look of horror on her face, she could almost look as if she were sleeping. Wrapping her in his arms, Rhaegar finally allows himself to cry. Loud, long sobs that make him shake.
He'd wanted to give her the world, not lose his along with her. His lips touch her frosty ones. Rhaegar kisses death like he's never kissed anyone else, wild and raging and too full of emotion. He is not completely careless, but it doesn't matter, because her waxen flesh cannot bruise. "I'll not leave you here, love," he whispers into her mouth, stroking her dark tresses.