Will only kill if they have taken money

"There is only gold and steel"

In training, they are paired with another trainee, at the end of the training, one must kill the other to graduate and become an Assassin, the last impediment to the turning of their heart to stone is the slaying of one who is dear to them.

They wear the Black

They wear the sign of the Black Dagger on their forehead when on contract

The proper title of respect is "Killer"

Gold from an Assassin is called "Black Gold", or "Blood Money", most will not accept it, it is considered tainted.

The killing dagger hilt is inscribed with "I have sought him, I have found him", left in body.