Truth candles were purple in color and intended to be burnt in ten-minute intervals. The longest-lasting candle that could be made burned for ninety minutes. This was the third type of candle mystics learned to make when studying candle magic.
After burning for the desired amount of time and then being extinguished (either by blowing, snuffing, dousing, or reaching the end of its wick), the victims had one chance to resist the candle magic. Those that succeeded in resisting felt nothing and were not affected. Those that failed fell into a stupor and would answer truthfully to questions posed to them. They were forced to answer two questions for every ten minutes the victims were exposed to the truth candle. While in this state of torpor, subjects could only defend themselves—they could not take any offensive action and they could move at only half their normal pace. This trance-like state lasted somewhere between twenty minutes and two hours, after which the victims recovered completely.
The victim(s) had to remain within ten feet (three meters) of the burning candle for the entire time it was lit and when it was extinguished, or that application of the candle was wasted.