Aja Mask

To the eye the artifact looks much like any Stone Mask, since it is one at heart. The difference lies in Kars' handiwork: he reworked the mask so the Red Stone of Aja would sit in the opening set over the brow, letting the gem power the transformation the plain mask never could. The result is a relic bound tightly to his single ambition, mastery over the sun.

In essence the Aja Mask is a far stronger Stone Mask. On a Pillar Man it bites clean through the skull just as the original does to a human, but instead of merely enhancing its wearer it carries them all the way to the Ultimate Lifeform. Kars designed it precisely so the Red Stone of Aja would trigger the mask's power, and it did so only when struck by ultraviolet light. At the height of Battle Tendency he lets the sun's rays fall on him while wearing it, and the very radiation meant to destroy him instead activates the stone, remaking him as a being immune to sunlight and no longer a Pillar Man. The mask is consumed in the act.

Kars is the only one to don the Aja Mask. Millennia earlier he, Esidisi, and Wamuu had tested the Stone Mask on countless captives, and it was Kars who realized the Red Stone of Aja held the key to conquering the sun, hoarding the mask through his long hunt for a gem powerful enough to finish the work.