Mavin's earthfast

Mavin's earthfast was a 10th-level Arcanist spell 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.