The Slaughter Note (さつりく帳) is a book in Mahou Shoujo Site.
It's a dark red note book with the words "Slaughter note" written on the front. Inside the book displays pictures of the magical girls. Behind the pictures, the names and addresses are written.
The second owner of the note, Rina Shioi, used the note to kill Magical Girls for their sticks. She was called the "Magical Hunter" during this time period.
Nana was the one who gave this notebook to each of the girls.