Source: What Lies in Dust, pg(s). 84-85
An idol is a statuette that, serving as the focus of cultic worship, has come to embody a measure of magical power. Idols are effectively inanimate statues, but have powers and can share spells with nearby allies. 
Stone idols are found as ancient carvings in long-lost ruins, and fascinate explorers with inklings of lost glory. They can store memories, as well as frustrate some kinds of divinations.