Desynthesis Endgame Guide

[Teiren]

Mastercraft Demimateria can't be obtained from Heavensward items. Fieldcraft Demimateria III likely comes from Disciple of the Hand tools at or near level 60. However, I don't know why you're asking this. If you want those two demimateria, it'd be a lot easier and less expensive to use the same ARR items as always.

Oh, or maybe you're asking what they're used for in Heavensward. The patch notes have the new recipes, and some of them do use Fieldcraft III and Mastercraft.