Zandalar Demoniac's Robe

Zandalar Demonia Robes are cloth chest armor with heavy stamina usable only by Warlocks. It also increases damage and healing done by spells, and increases spell hit chance. The robe is part of the armor set called the Demoniac's Threads.

Source
The robe is a reward for the quest given by Al'tabim the All-Seeing on Yojamba Isle in Stranglethorn Vale.