Human Frailty

The single black mana buys destruction with no qualifiers at all (no "nonblack," no "creature an opponent controls," no damage cap a fat body survives) except the one printed in the name: the target has to be Human. That trade inverts how removal is usually priced. A generic one-mana kill spell sets its rate against the breadth of legal targets; this one costs almost nothing precisely because it reads as a blank against half the boards it sees. The discount is a wager that you will face enough Humans to cash it, the same arithmetic that makes a tribe-hosing instant cheap in a vacuum: the cost reflects how often the condition is met, not how strong the effect is once it lands. This sits in black's long habit of selling unconditional destruction below market in exchange for narrowing the target pool, and the line it draws is unusually sharp. Against a board of Humans it is about as efficient an answer as the color prints; against anything else the text resolves to nothing, a removal spell that exists or doesn't depending entirely on who is looking back across the table.