SiluriansThe Silurians are a reptile-like humanoid race that inhabited the Earth long before the human race. They first appear in the Third Doctor adventure, Doctor Who and the Silurians, where they are awoken from their self-induced hibernation by the energy from a local nuclear power research centre. The Silurians release a deadly virus and attempt to disperse the Van Allen radiation belt in an attempt to take the planet back from the humans, but are thwarted on both attempts by the Doctor. The Doctor attempted to barter a peaceful solution where both Silurians and Humans can co-exist together, but the Silurian base is destroyed by UNIT.
The Silurians were next seen alongside their aquatic cousins, the Sea Devils, in the Fifth Doctorís adventure, Warriors of the Deep, in which both races worked together to reclaim the Earth as theirs. The Doctor tries to prevent any bloodshed between the Humans and the Silurians (and the Sea Devils), however he is unsuccessful again when his companion, Turlough kills the last remaining Silurian on Sea Base 4.
The Silurians were next seen in the Eleventh Doctor two-parter, The Hungry Earth and Cold Blood (Series 5 : Episode 8 & 9) when another colony were awoken from hibernation by the drilling operation being carried out underground. These Silurians lacked the third eye (see picture above) that the previous Silurians had and wear masks. The Silurians misinterpret the drilling operation as a deliberate attack on them and take hostages, including the Doctorís companion, Amy. The Doctor tries, again, to negotiate a peaceful co-existence between the two races, but is foiled again when a war hungry Silurian provokes a panicking mother to kill her. However the Silurian Leader recognises that in the future, it may be possible for Humans and Silurians to co-exist peacefully and allows the Doctor to return to the surface of Earth.
In the 2011 Series 6 mid-season finale, A Good Man goes to War (Series 6 : Episode 7), the Silurian Madame Vastra lived peacefully in London, after being found by the Doctor some time previously. Vastra had been bent on revenge after her Silurian sisters were killed during the drilling of the London Underground network, but the Doctor found her and calmed her down and allowed her to live above ground in London. In 1888, after killing and eating Jack the Ripper, Vastra was called upon to repay that debt to the Doctor when he went to war at the Battle of Demonís Run to save Amy. Vastra, along with her maid, Jenny, went to battle with the Doctor and assisted him in taking over Demonís Run, along with many other Silurian warriors, presumably recruited by Vastra. Vastra refers to the Doctor as her friend, indicating that although the Silurians have previously been seen as mainly villains, that some members are capable to being friends with other species.