It was a reward that you could pick during Treasures of the Kotl City in 2016
you could turn in the KOTL drops and get it
and were only available until Treasures of the Sorcerer's Dungeon started in 2017
right now is actually the last time you can turn in those artifacts
(Doom, KOTL, & enchanted origins into the researcher at Sorcerer's Dungeon)
(Cult artifacts to the researcher at Khaldun Encampment)
when Pub 106 goes live, the researchers will be gone