How to get Diadem of the Spell-Keeper head transmog in WoW

Diadem of the Spell-Keeper is a transmog appearance for the head slot, unlocked by

Diadem of the Spell-Keeper: A crown once worn by head-slot transmog radiates with the

rays of aton slot Diadem of the Spell-Keeper Head-slot Transmog; Wings of Awakening Back-slot Transmog in 5 Color Variants; 30 Days of Game Time TAKE WING TO A NEW BEGINNING

lord of ocean slot Diadem of the Spell-Keeper Head-slot Transmog Returns you to Hearthstone Location> Diadem of the Spell-Keeper Head-slot Transmog 30 Days