Ok, this is a Buffy the Vampire Slayer/Harry Potter Cross-over. It starts immediately at the end of book 5 of Harry Potter. All your faves from both realms come into play as well as Lily, James and Sirius.

FLASHBACK

Only one pair was still battling, apparently unaware of the new arrival. Harry saw Sirius duck Bellatrix's jet of red light: he was laughing at her.

'Come on, you can do better than that!' he yelled, his voice echoing around the cavernous room.

The second jet of light hit him squarely on the chest.

The laughter had not quite died from his face, but his eyes widened in shock.

Harry released Neville, though he was unaware of doing so. He was jumping down the steps again, pulling out his wand, as Dumbledore, too, turned towards the dias.

It seemed to take Sirius an age to fall: his body curved in a graceful arc as he sank backwards through the ragged veil hanging from the arch.

Harry saw the look of mingled fear and surprise on his godfather's wasted, once-handsome face as he fell through the ancient doorway and disappeared behind the veil, which fluttered for a moment as though in a high wind, then fell back into place.

END FLASHBACK

Sirius was soaring through the cold air and landed hard on the flat of his back on a cool, marble floor. Sirius lay on the ground for two minutes, gazing up at the high ceiling until he was roughly brought to his feet by a shifty-looking character in a cream linen toga, Roman style, with an air of authority. He…he…Sirius squinted to capture the man's image. The man had blue and gold skin! His eyes were large and a surprising shade of blue. His hair was gold, and cut short.

'You have a lot of faith…' began the man, pensively, as he stood over Sirius's body on the ground. He didn't seem to be unsettled by Sirius's abrupt arrival; in fact, he seemed to have been waiting for him, although Sirius had no idea where he was, or what the peculiar man was here for.

'Where am I? What happened to the others? How do I get back?' Sirius demanded, alarmed. The blue and gold man raised an inquiring eyebrow, but otherwise, looked distressingly calm.

'Eager to leave already, are we? After daring to enter our realm? You are most disrespectful, mortal.' Sirius looked around, confusion creasing his brow.

'What the bloody hell are you on about? Whose realm? What realm? And what is up with your skin?' Sirius was getting freaked out now.

'You should know. It was you who came to us.'

'And you are?'

Another figure appeared. It was a female, dressed the same as the weird man. She had black hair up in an intricate design that was very ancient roman. She stepped out from behind a large white marble pillar.

'We are the Oracles, mortal. You entered our realm. Have you no gift for the Powers?'

Sirius stopped and stared at her. Oracles? His mind cast back to when he was a student at Hogwarts. He and James had taken Divination together, and hadn't paid that much attention to the Professor….. Could this be real?? How could he get back?