If you need potent dust, just keep tributing the artifact of the immune, it has a common chance to give you 25 potent dust and a rare chance to give you 10 amber.

There is also a chance that you can find nirvana tonics in dungeon chests.

bonus: there is a very low chance that you can find a "Rockwell Recipes: Nir---a Tonic (torn)" from tributing the artifact of the immune.