Idle Basalt appears on the 3rd and 4th floors of Marukyu Striptease within the Midnight Channel. While it is pretty unremarkable, it will usually be accompanied by a Persistent Fuzz as a deterrent to multi-target elemental attacks, since it will repel them. When defeated, it may drop Idle Stone Iron. Selling 6 Idle Stone Irons at Daidara will unlock the Black Stone Mail male armor.
In Golden, Idle Basalt appears on the 1st to 4th floors of Marukyu Striptease. It nulls Physical, is strong against Ice and Wind, and is weak to Fire and Electricity. It may also drop Lemon Quartz for trade at Shiroku Pub.
Persona Q: Shadow of the Labyrinth[]
Idle Basalt first appears as a scripted encounter behind a locked door in Stop 1 of the Group Date Cafe, 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 Electricity 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.
Idle Basalt later appears in Stop 4 of the Group Date Cafe. When defeated, it may drop Boulder Piece and Boulder Hand. Boulder Piece is used to create the Power Plate for Kanji, and the Kevlar Vest unisex armor. Boulder Hand is used to create the Furious Fists for Akihiko.
Persona Q2: New Cinema Labyrinth[]
Idle Basalt appears in the 2nd Block of the final Theater, the Theater District. It attacks with heavy Physical skills, and may Petrify a target. When defeated, it may drop Basalt Cache and Basalt Diamond. Basalt Cache is used to create the Tom Sawyer for Morgana, the Samonji for Yusuke, the unisex Kaiser Armor, and the Solar Dog Suit for Koromaru. Basalt Diamond is used to create the Illuminati for Mitsuru.