Idea for evil creature thingy:

A meteor falls to earth. Inside is near-microscopic creature and some black goop. The black goop spreads a highlycontagious virus. The infected are only weakened to begin with, giving them time to spread the virus.

In the later stages, the victim is slowly decomposed, turning into the same black goop.

The goop is a concentrated form of nutrients essential to the organism in the meteor. The creature uses the black goop in a form of photosynthisis to generate eletricity to stimulate the goop into movement.

As more people are infected, more goop is created and the creature grows in mass.