Trod

The Trods were a race of cone-shaped robots that ran on static electricity, led by the Super Trod.

Characteristics
Robotic in nature, the bodies of Trods were dustbin-shaped, vaguely resembling the casings of Daleks. Their cone-shaped head sported a single eye and a mouth, with a long antenna at the top. The head itself was encircled by a silver tube atop a neck which connected the head to the body. Analogous to the Dalek weapons platform, this rim sported a silver mechanical arm with three fingers at both sides. Between the arms in the center was a silver energy weapon, similar to the Dalek gunstick, which could stun or kill humanoids (COMIC: The Trodos Tyranny) and even blow apart Dalek casings. (COMIC: The Trodos Ambush) At the bottom of their bodies were motor tracks which allowed for transport. (COMIC: The Trodos Tyranny, Return of the Trods)

Originally, the basic Trods had a dark silver coloured head and neck atop a black body which allowed Trods, who numbered in the hundreds at least, to be distinguished by sporting the number of individuals, written in yellow. Above the basic Trods was the Super Trod, who was distinguished by its yellow head and body. Rather than a number, the designation "Super Trod" was simply written in black on its casing. (COMIC: The Trodos Tyranny, Return of the Trods) In addition, a minority of Trods had yellow necks. Later in their history, Trods lacked distinguishing numbers. (COMIC: The Trodos Tyranny, Pursued by the Trods, The Trodos Ambush)

History
In 2066, the Trods were constructed on Trodos by MacTaggart to give himself power over the other colonists, secretly using them to enslave everyone. When the First Doctor, John and Gillian arrived on the planet, they were captured by the Trods, but escaped and deactivated them. (COMIC: The Trodos Tyranny)

Some time later, the Trods were reactivated by another space traveller who took control of them and used them to capture the Doctor, John and Gillian. After their new Master died, the Doctor commanded the Trods to enter a furnace room, destroying them. (COMIC: Return of the Trods)

Dr. Who and Jason failed to prevent the Trods from destroying Arcalis. (PROSE: Head Games)

The Trods constructed their own space-time machine and pursued the Second Doctor, John and Gillian to prehistoric Earth, where the Doctor used mammoths to destroy their power supply. (COMIC: Pursued by the Trods)

Centuries after the first encounter, the Doctor returned to Trodos to make peace with the Trods. The Daleks found out about this meeting, massacred the Trods, and waited to ambush the Doctor when he arrived. The Doctor, John and Gillian found the surviving Trods and joined forces with them to battle the Daleks. This allowed the Doctor and his grandchildren to escape in the TARDIS. (COMIC: The Trodos Ambush)

Hollow models of the Trods were once on display in a Time Museum. They were marked as "Space warmongers for generations", implying they had a wider history outside of fighting the Doctor. The Doctor, John and Gillian hid from Cybermen inside the models. (COMIC: The Time Museum)

The Fourth Doctor later told the Hornets that they were not as much of a threat to Earth as the Trods, Pescatons, Vogons or Krynoids. (AUDIO: A Sting in the Tale)

Behind the scenes

 * The Trods were created for the TV Comic strip as surrogate Daleks, since the rights to the Doctor's arch-enemies had been sold elsewhere at the time – namely to City Publications, who produced TV Century 21 in which the comic strip The Daleks was appearing. Oddly, the 1968 TV Comic Annual featured the Doctor in one story with the Daleks and in another with the Trods. (COMIC: Attack of the Daleks, Pursued by the Trods)
 * Their appearance as empty shells in The Time Museum is an obvious parody of a Dalek shell appearance in The Space Museum and the plot of Pursued by the Trods is highly similar to that of The Chase.