The Matchstick Key is the first key that appears in Locke & Key. More or less, it ignites fires, fast. Mark has it at the very beginning of the show. After finding out that Rendell has died, he kills himself with it so no one can get in his head, as he had been entrusted with knowing the key's locations. Later on, Dodge tracks it down and gives it to Sam Lesser, who uses it to break out of prison.