Doctor Who is known for its long list of monsters, which is ironic given that series creator Sydney Newman was originally in opposition to them. As reported by CBC, Newman requested that there be "no bug-eyed monsters" in the series. Luckily, he relaxed his stance early on, paving the way for a bevy of fantastic and terrifying monsters to take center stage in numerous Who episodes.
Yet, many of these monsters have largely been forgotten by fans down through the decades. As the series approaches its sixtieth anniversary, fans might want to take a trip back through time to appreciate these underrated monsters. The door is open for them to return in future Who stories, but nothing is certain at this point in time.
The Yeti
The robotic Yeti were manipulated by the entity known as the Great Intelligence, and were a key Doctor Who monster during the era of the Second Doctor. After several encounters, the Yeti essentially dropped off the map, showing up again in the pivotal Fifth Doctor special serial "The Five Doctors."
These Yeti attempted to disguise themselves with fur, and came in several variants. The Second Doctor encountered what he dubbed the "Mark II and III" versions of the creature, the latter of which was capable of wielding weapons. Their most clearly defining characteristics were their monstrously intimidating appearance and blood-curdling roar.
The Mara
The Mara was an ancient entity that plagued the Fifth Doctor's companion Tegan throughout her time on the TARDIS. It was a notoriously difficult monster to classify, since it had no true form, existing in the space between thought and reality. It attempted on several occasions to take physical form inside the known universe.
Both times, the Doctor was forced to do battle with the Mara, until finally destroying it by trapping it inside a circle of mirrors, where it could not escape its own horrific snake-like visage. Whether the Mara will ever return remains a mystery, but it certainly made for one of the most chilling Doctor Who stories of the classic era.
The King Vampire & The Three Who Rule
The Fourth Doctor's trip to E-Space was filled with adventures that also revealed a few interesting revelations. One of these occurred during the season 18 serial "State of Decay," where the Doctor and Romana squared off against a trio of vampires known as The Three Who Rule.
These vampires used to be human astronauts but were corrupted by the powers of the King Vampire, who just happened to be an ancient and deadly enemy of the Time Lords of Gallifrey. The Three Who Rule were vanquished alongside their vampiric master, and have largely been forgotten in the annals of Who history.
The Krynoids
Carnivorous plants make for interesting stories, and the Krynoids were certainly at the top of the pile. They made their debut in the season 13 serial "The Seeds of Doom," squaring off against the Fourth Doctor and Sarah Jane Smith.
The trouble began when an eccentric plant enthusiast tried to procure an extraterrestrial seed pod from an Antarctic expedition, inadvertently releasing the Krynoids in the process. These ravenous plants traveled from world to world, devouring all life in an attempt to dominate and flourish, free from predators.
The Raston Warrior Robot
The Raston Warrior Robot is one of the coolest Doctor Who monsters to show up for five minutes, before disappearing into the ether. It made its debut in "The Five Doctors" when Sarah Jane Smith and the Third Doctor stumbled upon it while fleeing a pursuing pack of Cybermen.
Known for its deadly accuracy and blinding speed, the robot was considered the most deadly assassin in the known galaxy. The Third Doctor used that to his advantage by luring the fearsome fourth-generation Cybermen into the kill zone, allowing the robot to slay them all with lethal efficiency. It was never seen again.
The Gelth
The Gelth were revealed in the first season of the 2005 Doctor Who reboot as specters that survived in gaseous environments. The Doctor quickly identified them as an alien race who were able to take refuge in human corpses, allowing them to survive in an otherwise hostile environment.
Unfortunately, the Gelth were a malevolent and manipulative species who preyed upon the Doctor's guilt over the damage done by the Time War, in order to gain a foothold into the physical realm. After being banished back into the void by the psychic powers of the human known as Gwyneth, they were never heard from again in the mainstream series.
The Sycorax
The regeneration of the Ninth Doctor into the heroic, yet tragic Tenth Doctor was a landmark event for Doctor Who fans, signaling the end of the first season of the returning show. David Tennant would make his debut as Ten, who is forced to battle the deadly Sycorax, while also dealing with the aftermath of a chaotic regeneration cycle.
Eventually, the Sycorax were driven off of Earth after the Doctor beat them at their own game, but then-Prime Minister Harriet Jones ordered Torchwood to obliterate their ship as a demonstration of strength. The Doctor was enraged by the slaughter, but the Sycorax themselves have yet to make a reappearance, either for the sake of vengeance or otherwise.
Fenric & The Haemovores
The ghoulish and ghastly Haemovores encountered the Seventh Doctor and his companion Ace in the classic serial "The Curse of Fenric," which served up a double dose of horror. Despite their frightening appearance, they were actually the future descendants of humans who had undergone a genetic mutation.
Though not vampires by strict standards, Haemovores possessed several comparable traits, including superhuman strength, telepathic persuasion and resistance to many forms of damage. They could only be slain by a stake through the heart, and they were susceptible to psychic barriers derived from a strong faith. To date, they've largely been forgotten, and arguably deserve a second round.
The Mechonoids
The dreaded Daleks have very few enemies that can stand shoulder to shoulder, and act as a credible threat. The Mechonoids are one such race, though they didn't last very long before getting mothballed. They made their debut in one of Doctor Who's best Dalek-themed episodes "The Chase," where they did battle with a pursuing contingent of Daleks, destroying several in the process.
Originally a collection of robots in service to humans, the Mechonoids later grew self-aware and forged an empire of their own that was considerable in size and scope. Later Doctor Who material has expanded on their story over the years, but the creatures have yet to make a second return on television.
The Vervoids
The Vervoids were first introduced in the massive multi-episode epic known as "The Trial of a Time Lord," which took place during the Sixth Doctor's run. Their story was a self-contained serial that was intended to be evidence in the Doctor's defense, yet ended up being turned into an argument for genocide.
Indeed, the Doctor did end up destroying these plant-based creatures when they attempted to free themselves from their status as an artificially created slave species. Their intent was to annihilate human life, forcing the Doctor's hand in the process. They remain buried under the complex timeline of the Sixth Doctor's trial, while fans pine for the sinister Valeyard to make a reappearance.