A sign to the audience that a character is about to die, and/or otherwise foreshadowing an imminent bad end.
A death flag is usually raised by a character saying or doing something that can be seen as tempting fate. Examples include: Doing something that he or she has been warned, sometimes repeatedly, could be fatal; an unrequited relationship suddenly and finally being requited, especially if it comes out of the blue; a promise to return just before leaving on a journey of uncertain length; and so on.
