To Break the Pillars of Heavens
Legend is an interaction between the Chaos of the Overworld and the physics of the World. Frequently, it’s thought of as a being’s deeds and resulting reputation; that’s an aspect of it, but it’s more than that. It’s an informal measure of a divine entity’s power and ability to change the three Worlds. It is not known how the spirituality of the Underworld fits in, but Legend works there just as well as anywhere else.
Legend provides a metaphysical weight to a divinity, bending reality like a mass bends space. But, whereas bent space, as a Worldly process, simply makes gravity, Legend can have a variety of effects owing to its nature as an Otherworldly process.