The
Vahnatai are the most
ancient of the
civilized species in the
Exile/
Avernum series of
adventure games. They live in the deepest caverns, where they carry out a particularly curious
survival strategy: they live actively for several centuries, depleting the available
food supply, then go into a sort of
hibernation for several centuries more, during which time the fungus they eat can grow back.
The Vahnatai are quite fond of crystals, which they employ extensively in their curious form of magic. They are capable of storing information, up to and including the soul of a creature, in crystalline form. Lesser crystals can store messages, or teach skills. More powerful ones can capture creatures' souls for later summoning, or store a person's soul and personality whole and entire. When a Vahnatai elder dies, his or her soul may be stored in crystalline form; the result is known, unsurprisingly, as a Crystal Soul.
The events of the war between the Vahnatai and the Empire occupy a great deal of the plotline of Exile 2 (aka Avernum 2) and Exile 3.