Astral Plane

The Astral Plane, also known as the Astral Sea, is a plane of existence beyond the Material Plane.

Lady Allura told Vox Machina, during a conversation on how to dispose of the Horn of Orcus they had acquired, that when a Bag of Holding is destroyed, its contents jettison into the Astral Sea.

When Scanlan Shorthalt scried through his magical poo, his consciousness transcended the Material Plane, traveled across the Astral Sea, and arrived at his scrying destination on the Material Plane.

Creatures
Many beings reside within the Astral Sea, although Lady Allura only mentioned one:
 * Githyanki
 * Astral Dreadnaught chained by Halas Lutagran
 * Zehir, the Cloaked Serpent