Sasaeru

Sasaeru (支える, Japanese for Sustaining) is one of the seven Kyūtai forged by an unnamed Kidō master centuries ago. It is believed to be the strongest of all the orbs and holds within it the power to make the wielder stronger than a god, if legend is to be believed. Its location is currently unknown, though people have been searching for it for generations, though all with little luck.

Behind the Scenes
This is influenced greatly by the seven Ka'kari in the Night Angel Trilogy of novels.