Disclaimer: I don't pretend I own HP or ever will.
AN: This is a response to the mirror of Erised challenge, set up by PrimroseAmelia.
Severus Snape angrily stormed into the disused classroom. As if it wasn't bad enough that Quirrell had refused to talk to him about WHY he was trying to get past Hagrid's pet Fluffy, now nightmares of Lily's death had started to haunt him once more.
Smoothing down his robes, he decided to look around and gain his bearings. It was then that he noticed the mirror propped against the wall, bearing the inscription Erised stra ehru oyt ube cafru oyt on woshi.
"I show not your face, but your hearts desire." He murmured. His curiosity aroused, he decided to take a closer look. As his eyes met the mirror, he gasped in surprise.
Standing next to him in the mirror was his old friend Lily Evans and she was smiling at him. Her hand was entwined with hers in the mirror and in front of them stood a boy about the same age as Potter. The boy looked exactly like a younger version of himself, except for one small detail. Instead of Severus Snape's empty black eyes, they were bright green, Lily's eyes exactly. My son, Snape realised to himself with surprise. And peeking shyly from behind Lily was a little girl, no more than three or four years old, with short black hair, just like him and she too shared Lily's green eyes.
But it wasn't what had really happened. In the real world, James-b$%$$#-Potter had married her and it was James-b$%$$#-Potter who's son she had given birth to, not his. With a snarl of anger and grief, he spun round on his heel and left the mirror behind. His hearts desire it might be, but it was crueller than any Death Eater.