Doctor Who: EVERY NuWho Villain And Monster Ranked Worst To Best

Appears in: Praxeus.

WhoCulture has covered the devastating effects of Praxeus in various lists in the past (like the one below).

This alien pathogen, which targeted the microplastics in humans, was brought to Earth by Suki Cheng, a scientist from another world. After her planet was devastated by Praxeus, Suki was tasked with finding an antidote. She discovered Earth was full of plastic and therefore saw it as the perfect laboratory - experimenting on Adam, an astronaut infected with Praxeus.

But while he was cured, Suki eventually succumbed to the deadly bacteria.