The Nethercoat is a magical yet elegant dress woven to include the Dusk of the Dead into the threads. While it provides no protection from traditional weapons, it does provide protection from magic. It will be very useful to Scarlett when she finally confronts Victor, since it will reduce the damage his magic inflicts.
Scarlett will obtain the Dusk of the Dead from Princess Chiamaka after their confrontation in the Necropolis in the Juma Tribal Lands. She will need to return to Jarta in the village of San Pasquale where she began her quest in order to weave the dust into a lovely dress. Obtaining this dress is a prerequisite for entering the Palace.