warlock

"No, we [kill] for the money. And, because we above all must know the value of a human life, we do it for a great deal of money.
There can be few cleaner motives, so shorn of all pretense. Nil mortifi, sine lucre. Remember. No killing without payment."
He paused for a moment. "And always give a receipt,' he added."
-- Dr Cruces of the Assassin's Guild, Terry Pratchett, Pyramids