Changing the past indirectly causes the death of the one who changed it.
Needs a Better Title - Suggestions: "Time Travel Duplicate Exclusion Principle" A character travels back in time and changes the past for good or bad, and then explicitly dies as an indirect result, rather than vanishing as part of a Delayed Ripple Effect or sticking around. The reasons for doing it this way might vary. One reason might simply be to have a Time Travel plot involving a visitor from a Bad Future and/or a Heroic Sacrifice but without changing the status quo, either by killing a major character or harming their Uniqueness Value; another reason might be to provide all the drama of killing a major character without harming someone with Contractural Immortality (see Expendable Clone). Having multiple copies of a main character might just be confusing, too, so this also deals with that possibility. For a trope which doesn't necessarily involve Time Travel but still treats multiple copies of a character as expendable, see All The Myriad Ways. Not to be confused with Clock Roaches and Time Police, which don't count because if they kill you, it is for all practical purposes a direct result of changing the past. If a character dies attempting to change the past, but merely causes a Stable Time Loop, that's You Already Changed The Past. As with all Death Tropes, these examples will most likely contain spoilers.