Zandalar Illusionist's Mantle

The Zandalar Illusionist's Mantle is a cloth shoulder armor for mages which gives a bonus to stamina, intellect, spirit, and overall magical power. The robe is part of the armor set called the Illusionist's Attire.

Source
The mantle is a reward for the quest Paragons of Power: The Illusionist's Mantle given by Al'tabim the All-Seeing on Yojamba Isle in Stranglethorn Vale.