Cyber-pollen
From Tardis Wiki, the free Doctor Who reference
Cyber-pollen was a chemical that, upon coming in contact with dead organic matter, converted the bodies into Cybermen. Cyber-pollen was released from each exploding Cyberman sent out by Missy in the form of rain, and was situated over graveyards. Missy then planned to use the rain to kill all of Earth's remaining population and convert them as well. (TV: Death in Heaven)
