Swenyo

Swenyo was a rare ore found on few planets. One of these planets was the planet Callous. It had the rare property of giving off psychic energy which could be used in battle computers. (AUDIO: Sins of the Father)

One of the few places it could be found was the Callous where The Master manipulated people and events to get a large deposit of it for the war effort.

When trying to mine the ore, races like the Ood were vulnerable to it and got driven insane by it. (AUDIO: Sins of the Father)

Even Time Lords were affected by it, finding it uncomfortable. (AUDIO: The Persistence of Dreams)