You get the Idol of Fear from a spirit (a red wisp) in Stonebrunt after handing him a Grimy Lance (dropped by a Tae Ew Spiritualist in The Feerrott. Quest description by Imothep at the Grimy Lance item page: Give the lance to the spirit, get the Idol of Fear (no rent!), follow the spirit's human form to the cat village to kill Disciple Orokate. After Orokate's death his ghost appears. Hand him the Idol of Fear for the reward: The Soulfiend Lance.