Mavin's earthfast

Mavin's earthfast was an arcanist spell of epic power used in the days of Netheril.

Effects
The spell was originally created to allow continued mining of areas that would otherwise be too dangerous to mine. A casting of Mavin's earthfast made large areas of underground tunnels impervious to cave-ins and similar disasters. Its use was later adapted to preserve important areas of cities.

Components
The components needed for this spell were a stone of controlling earth elementals, six chardalyns (each imbued with transmute mud to rock), and an earth elemental.

History
The spell was created by Mavin around -510 DR (3349 NY). However, after the near-cataclysmic destruction of the Weave caused by the casting of Karsus's avatar in -339 DR (3520 NY) and the subsequent restrictions placed on magic by Mystra, the spell could no longer be cast. Later ages remembered the spell simply as earthfast.