The Hunger

The Hunger was a genetically engineered swarm of bacteria and archea which had been tweaked to perfection as relentless killing machines, devouring anything in their path.

Biology
The Hunger was artificially created in a lab, mixing together ordinary yeast cells with the omnivorous microbes from Pluto, the most voracious bacteria in all the cosmos. Their hibernation mechanism was removed, purging them of rest and leaving them as nothing more than monsters with an insatiable appetite for destruction and carnage. They appeared as a giant swarm of tiny black dust bunnies. They were contained within an electromagnetic field that rendered them defenseless (K9TV: Black Hunger)

History
The Hunger was created by Inspector Drake to resolve London's litter crisis, but they got out of hand when Darius interfered, using them to clean up the mansion. His attempts to return them resulted in disaster as they broke loose and headed for the open, where, if left to their own devices, they would consume the entire globe. K-9 managed to defeat them by imprisoning them within his own body, burning his fuel cells to create an electromagnetic pulse that reversed their polarity and sucked them into his "stomach". There they stayed at least until he could dispose of them properly. (K9TV: Black Hunger)