Harbinger

Omen or Portent, often bad

Don’t come all in here like the harbinger of doom!

Dating as far back as the 14th century, the harbinger was an army officer sent out in front of the army to arrange for places for the troops to sleep. At the time such lodgings were called “harbor”.  Often the arrival of the harbinger would lead to a panic amongst the citizenry because the army was not far behind and that meant taxes would be collected and a ton of pillaging would be occurring. Hence the generally negative aspects of something be a harbinger.

There can still be a positive aspect to the term such as a “harbinger of spring, but the gloom and doom usually wins in the end!