Asgorath's Ban

Asgorath's Ban is the magical barrier surrounding Divostra that prevents entrance into the plane by foreign interplanar beings. The casting of Asgorath's Ban marked the end of the Titanomachy, after the dragon gods Asgorath and Bahamut, along with the metallic dragon flights, joined forces with the refugees from the Feywild to defeat the Primordial Titans and banish them to the Elemental Planes. Asgorath summoned all of its power to cast the spell, sacrificing its corporeal form in a shimmering cloud of thaumaturgic energy that formed an invisible barrier around the edges of reality. Its sacrifice ensured that the Primordial Titans could never return to Divostra and wage another war on the mortal races.
When the violence of the Drow War weakened the stability Asgorath's Ban, it allowed Asmodeus to enter Divostra from the Nine Hells with his infernal hordes. However, the weakening of the barrier also allowed the Celestials to enter Divostra on the other side of the conflict and, with their help, Bahamut and the metallic dragons fought the forces of the Nine Hells, pushing them back into Baator. Mortally wounded, Bahamut sacrificed his corporeal form to re-cast Asgorath's Ban, though in his weakened state, he could only reinforce the barrier, rather than fully mend it. The Exotar honored the Platinum Dragon's sacrifice by remaining behind on Divostra, vowing to guard the remaining portals to the Nine Hells and ensure Asmodeus could not threaten the plane again.

Effect

Non-fae souls not that are native to the realm of Divostra cannot pass through the ban into the Prime Material Plane, which separates Divostra from other lower and higher dimensional planes. Any creature can pass through the barrier moving out of Divostra, but only fae creatures and souls native to the Prime Material Plane can return.
Something that Asgorath did not account for—souls of native Divostrans sent to the Nine Hells or the Abyss who then became powerful enough fiends could theoretically pass back through the barrier, so long as they still maintained a strong enough connection to their previous existence.
The only beings capable of shattering the barrier are the other two prime Draconic dieties, Bahamut and Tiamat. Bahamut sacrificed himself to reinforce the barrier following the Drow War, and Tiamat is currently imprisoned on Avernus following her battle with Moradin during the Drachomachy, still recovering from her near fatal encounter with the Dwarven diety.

Manifestation

The barrier is invisible and only can be seen when non-native creatures are actively attempting to pass through it, at which point it appears as a shimmering bend in the fabric of reality. When a portal opens between the Prime Material Plane and another dimensional plane and a creature attempts to pass through it, they will find themselves pushed back by this translucent wall, as if they were pushing against a flat surface of solid rubber.

Related Deity/Higher Power

Asgorath

Material Components

An ascended creature whose essence has become part of the Thaumic Weave of Divostra, whom the spell consumes.

Gestures & Ritual

The caster needs to speak the ancient draconic chant first uttered by Asgorath and form a perfect circle with their arms.

Related School

Abjuration

Effect Duration

Until Dispelled