Date of Birth: 1473.
There's nothing in the history books about Il Carnefice, so I did a little digging in Abstergo's mainframe. Here's what I found: "A natural ally for the Borgia, Il Carnefice kills to the roar of an approving crowd."
The other small piece of information I could dig up is that he fancies himself as some sort of twisted artist. I guess that explains the crowd bit. I wonder if he performs tricks while doing executions, or whether it's all in the subtle way he pulls the lever?