Marika declaring the intent to search the depths of the Golden Order concides with Radagon leaving Rennala for Marika. Incantations and Sorceries all derive from the Greater Will, and Fundamentalism is both Faith and Academy with Law of Regression and Casuality being the laws that define the common divine origin of things from which all derive and all strive to return to.

>It is said that long ago,
the Greater Will sent a golden star bearing a beast into the Lands Between,
which would later become the Elden Ring.

>The fundamentalists describe the Golden Order through the powers of regression and causality. Regression is the pull of meaning; that all things yearn eternally to converge.

>The fundamentalists describe the Golden Order through the
powers of regression and causality. Causality is the pull between
meanings; that which links all things in a chain of relation.

As Ymir says, all are Stardust, and the study of light is the study of the influence of the Greater Will and the Stars. Starlight/Amber Starlight is the reflection of Fate writ in the skies, while the light of the Erdtree is the Fate of those bound to the Order.