Idyll is a major mountain on Pollux V, rising 5360 meters above sea level. Below it, there was the sonambutron of the Nauians who would wait in suspended animation the end of the planet's ice age.

Colonists would consider the mountain a mining resource, however it was guarded by robotic guardians.

The area around it was exceptionally stable tectonically and easy for mininc machinery to work in and the settlers mined for hafnium and other trace elements. However they noted that the deeper they dug, the more anomalous the variety of minerals seemed. (TOS video game: Star Trek: 25th Anniversary)