The CalderaBy Center-of-All Source: Planewalker Forums, October 26, 2004 Within the Plane of Ash lays a vast, dark lake. The lake’s waters, though darkened and chilled by the ash of the plane, are mysteriously pure and good to drink from. The water rests in the basin formed by a large, obsidian caldera. The caldera was once a roiling pocket of magma that burst and erupted like a volcano until the frigid, heat-sucking force of the Ash stole the pocket’s fire. It has since cooled enough to contain a large pool of placid water.