The Greatest Villains In Doctor Who, Ranked

The Doctor faces many alien creatures that assimilate or consume everything in their path. One of the most notable is the Krynoid, a large, carnivorous lifeform with an insatiable appetite. Born from eggs, Krynoids start out as fairly small beings, roughly the size of a house plant. When a living creature draws close enough, the Krynoid extends a tendril to make contact, infects them, and slowly transforms them into another Krynoid. They proceed to travel through space, devour the living things they come across, then move on to the next planet, to repeat the process. They're not invulnerable, however: Krynoids are unable to brave the extreme temperatures of certain environments, and are especially susceptible to the harsh conditions of Antarctica.

The Krynoid is a classic alien; clear comparisons can be made between this "Doctor Who" creature and those of "The Thing," "The Blob," and the "Alien" franchise. Many fans hope that this invasive weed-like being will eventually pop up on the current series. Sadly, this has yet to happen. The Krynoid simply hasn't shown up often enough to earn a higher spot on this list.