Lyrium

A valuable but dangerous mineral. In its raw form the ore will cause anything from serious injury to insanity in humans or elves. It will kill mages. Only the dwarves know how to process the ore to render it less dangerous and more useable. Generations of proximity have made dwarves more naturally resistant (not immune) to the effects. Surface dwarves lose that resistance over time. In its processed form, it may be handled by anyone, but long term exposure or a single mistake while working with it can lead to serious side effects such as emotional instability or complete psychosis.

Processed lyrium is used by dwarves and the tranquil to enchant items. The Circle of Magi also use it to mentally travel to the Fade in an aware state. Properly prepared, it can restore a mage's mana.