Resurrecting the dead

Sirius

Harry opened his eyes and saw he was in a room, similar to one in Grimmald place, but it had no roof- only a space of white light. At the desk, Sirius sat, playing exploding snap with James and Remus. Harry smiled. It was the first time he had ever seen all three marauders together...
He stood watching for a bit, completely invisible, until James and Remus left.
Then, he whispered the spell "Visabilous", which allowed Sirius, but only Sirius to see him.

"Harry?" Sirius asked, looking at him, "Why are you here? You're not dead yet?"
"Just visiting" Harry said, holding up the stone in his hand.
"You have never visited before!" Sirius replied slightly confused.
"I am going to do something which will destroy the Stone, which is my only way of contacting you. I just wanted to say Goodbye." Harry explained, not mentioning he would be resurrecting 3 people.
Sirius nodded.
"Thanks Sirius for everything you did in the year you were with me. You are like an uncle to me, and i'm so sorry I couldn't save you."
"No worries Harry, I was meant to die then. You did the right thing. Plus, i'm with the others now."
Harry smiled. "I haven't got long, so Bye Sirius" He said hugging him.
"Bye Harry, It was pleasure being able to spend my last year alive with you, rather than in Askaban. Thank you for that. Well done by the way, heard you defeated Voldy!" he said grinning
Harry grinned back, "Yeah, thought someone had to do it!"
Sirius Laughed, but then suddenly appeared deep in thought. "Harry, in my vault at Gringotts, there is a sealed letter, addressed to 'M'. Since I am no longer alive, and you are in control of my vault, will you send it for me?"
"Of course" Harry replied. " Whats it for?"
"Just something I should have said over 25 years ago, and now is my last chance" Sirius said seriously.
"Ok, Goodbye Sirius"
"Bye Harry, see you when your dead!"

Harry closed his eyes and thought of the next person on his list; Dumbledore.