The Voords resemble human beings, although they are not exactly the same - for one thing, they apparently have webbed hands and feet. As they always wear rubber wetsuits, it is difficult to say for certain. They arm themselves with daggers carried in a sheath on the hip, and they can be distinguished from one another by the symbols on their antennae - a circle, triangle, or something else. Only Yartek, the leader of the Voords, does not have an antenna on his wetsuit.
Yartek found a way to overcome the Conscience of Marinus, a machine which controlled and eliminated the negative impulses of the planet's population. He and the Voords robbed, exploited, cheated and killed the inhabitants of Marinus, who could not fight back. In order to prevent the Voords from taking over the planet, four of the five key microcircuits of the Conscience were removed and scattered across the planet. Had the Voords been able to capture the Machine, they could have controlled everyone's minds. But this was apparently not a very likely scenario, as centuries later, Yartek and his Voord followers had still had little success in penetrating the building where the Conscience was kept, much less in recovering the keys. They assaulted the building on a regular basis, crossing the acid sea surrounding its island in glass submarines, but never managed to enter it.
When the first Doctor, Susan, Ian and Barbara arrived on Marinus, they were captured by Arbitan, keeper of the Conscience. Arbitan also captured a Voord and destroyed it, but once he learned that the TARDIS crew were not affiliated with Yartek, he asked for their help in locating the keys. They successfully did so, but upon their return, they discovered that Yartek had managed to infiltrate the building and had killed Arbitan. Yartek coerced one of the Doctor's party into revealing that the final key had been obtained, and then tried to trick Ian into handing it over. Ian, however, realized that something was amiss and instead gave Yartek a fake microcircuit, which caused the Conscience to explode when it was inserted.
