Sirius Black
Sirius has sent off all the messages he wanted to. Now all he needed to do was find Peter. Kill Peter. Avenge James and Lily. Protect Harry.
How?
Sirius blinked.
If his Patronus could track down Remus and McGonagall to Merlin knows where, then it could certainly track Peter Pettigrew. On some other day, perhaps he would have given the Statue of Secrecy more thought but now, James and Lily are dead and today was All Hallows Eve. Muggles often ignore whatever magical or supernatural they see on this day.
"Expecto Patronum," Sirius cast, his thoughts on that very imaginative yet merry moment when he would finally have Peter at the end of his wand.
The silver fawn emerges again and Sirius thought this time, it looked downright sinister. Very fitting too, for a Patronous changed for Harry to track down the one who caused his family to die.
"Find Peter Pettigrew," he ordered. "Be visible all the time. Tell him Sirius Black will kill him."
The Patronous bowed and took off. Sirius summoned a broom- James's broom- and followed the streak of silver on the ground from the skies.