The Scourge Factory

The capsule was so small it evaded every detection system and radar as it entered the atmosphere and sunk to the depths of the Pacific ocean.

There, it released tiny machines (or were they creatures?) that started assembling, replicating and evolving into ever more complex and capable entities. In a few months, the scourge was building sprawling fabrication complexes in all the continents.

The drone was able to send an image of one of such underground factories before being disabled, a weird mix of technology and structures that could have been developed by humans, mixed with incomprehensible creatures and processes.