On Hidden Doors

A Tyrwinghan cosmological treatise, written in the DR 1600s, by Emyr of Tafolwern

On Hidden Doors is a forceful polemic by Emyr of Tafolwern on temporary planar connections. Emyr argues that elemental vortexes are part of a broader class of temporary planar connections, including uncontrolled or unpredictable fey crossings, and that planar drift helps explain why permanent portals sometimes appear or disappear.

Emyr called these unstable temporary connections planar upwellings.