There were a number of world afflicted with the low end probability called life.  Distance on a universal scale meant civilizations are almost always able to live, grow and die remembered only by the observations of the few beings powerful enough to do so.

Beings powerful enough to be called Gods, by any measure, though most would find the definition limiting. They tended to be unconcerned with the lives of the short-lived civilizations, most of which seem determined only to wipe themselves from their pain filled mortal coils.

Still, if preservation of mortals lives was low on the to-do list, then protecting the Universe  could be called their 9-5 daily grind.   

Any number of other universes may enter ours by a variety of means.  Also, more than a few advanced civilizations have lived long enough to develop ways of traveling to other planes of existences from this one.  So long has no threat was perceived, nothing was the usual course of action.

However, occasionally, entire worlds or Galaxies needed to be sealed or destroyed to prevent the spread of harmful beings or energies from outside the universe.

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The bell rang signaling the end of 5th period and the 4 minute warning to get to the last class of the day.  For Leon, it meant 5 minutes to get out of the school before the halls cleared enough for him to be noticeable.  Teachers had the strange habit of wondering why you are not in class whenever you are not in class.  A mystery that.

Outside the school, Leon Glances left towards what could, under the right circumstances, be called home.  Years of practice keeps his face neutral as he head to the right and to his part time job.  A general laborer for a man too cheap to hire real help, Leon was paid under the table to keep cost low and profits high.  It was way better than minimum wage though.  As for missing his last class, Calculus, it couldn't be helped.  He would fail it of course, but he would also be able to test out at the end of the year.  The school was generous when it came to trying to raise its number of graduates.

He was 2 blocks and 1 alley from work when the world changed.  Out of nowhere a small blue box appeared.  In the distance Leon could hear the sudden swell of car horns and what sounded like multiple crashes.  And why not? If you're driving and a part of your vision is suddenly blocked bad things are bound to happen.  Leon read the box in front of him.

       Attention [Sentient Beings]

This world has been sealed while [extra-universal energies] are incorporated into the existing structure.  Additional but non-essential information can be obtained from [Celestials].

Good luck