Author: Anlg
How to obtain:
Archfiend dye rolls every time you roll an archfiend dice or high class archfiend dice. When you roll a die, you first roll for the dye, then roll for other outcomes.
Archfiend dye has a 1/6,666 chance to roll from an archfiend dice and a 1/666 chance to roll from a high class archfiend dice.
Overall, it would take ~278 archfiend dice or ~42 high class archfiend dice on average to get this dye.

Method:
For normal profiles, you can buy dice from the auction house to roll.
The expected cost of the dye is 278 * (price of archfiend dice + 984,000) or 42 * (price of high class archfiend dice + 5,600,000)

Or you can obtain the dice from killing Inferno Demonlords.
It is recommended that you save the dice you drop until archfiend dye appears in a Vincent rotation for better chances of getting the dye.