Neglectful Precursors: Often played straight: see Black Box, Living Relic, Sealed Evil in a Can, etc. Of course, in fairness to them, most weren’t planning on going extinct or otherwise disappearing from the galactic scene.
This is a companion discussion topic for the original entry at https://eldraeverse.com/2014/07/03/trope-a-day-neglectful-precursors