Idle Basalt is a shadow that appears on the 3rd and 4th floors of Marukyu Striptease within the Midnight Channel. While it is pretty much unremarkable, it will usually be accompanied by a Persistent Fuzz shadow which will act as a deterrent to multi-target elemental attacks due to that shadow repelling them. Upon being defeated, it may drop the Idle Stone Iron material. Selling 6 Idle Stone Irons at Daidara will unlock the Black Stone Mail male armor for sale in the shop.
In Golden, Idle Basalt may also drop Lemon Quartz for trade at Shiroku Pub.
The first time the player encounters Idle Basalt is a fixed encounter behind a locked door in Group Date Cafe Stop 1, in a group of 5. They may pose an infuriating challenge due to their resilient defenses, ability to Power Charge their already painful physical attacks, and the Stona skill that will petrify a party member. Prepare party members with Electric and Light attacks to quickly dispatch them before they become a problem. Stona has immensely lower accuracy when targeting a guarding party member, so having frontline characters guard while a back row character repeatedly uses Hama or Mazio could be an effective strategy.
Afterwards, they are randomly encountered on Stop 4 of the same dungeon, to allow the player to farm materials required to unlock equipments in the Workshop.