Fanatic Tower is a sub-boss, found in the Yabbashah Block on the 85th floor of Tartarus. It impedes the player's progress and must be fought in order to continue. It later reappears as a normal enemy in Empyrean.
The boss battle with the Fanatic Tower is particularly troublesome as it is only vulnerable to Strike (though having increased evasion against Strike) and Wind magic, while resisting Slash and Pierce and reflecting Fire, Ice and Electricity magics. Akihiko is a good choice for this battle due to his Electricity resistance and Strike-based normal attacks. Yukari's Wind specialization may help in damaging this boss, but her weakness to Electricity hampers her usefulness in the fight. Bring protection against Poison since the Fanatic Tower's Poison Mist has stronger chances of connecting with Poison Boost.
The personas Mothman and Kusi Mitama can reduce damage taken from this Shadow (though Mothman's weakness to Pierce should be minded) while Take-Mikazuchi will nullify its Electricity attacks completely. A Thunder Charm accessory from Be Blue V can give Yukari the Dodge Elec skill for this fight.
Fanatic Tower appears in the 1st through 3rd Worlds of Magatsu Mandala within the Midnight Channel. It will buff itself and any accompanying shadows with Matarukaja and try to Silence the party with Foolish Whisper. After being defeated, it may drop a Ruinous Crown. Selling 10 Ruinous Crowns will unlock the Safety Belt accessory in the shop.
In Golden, it appears in Magatsu Mandala Worlds 1 to 3. It may drop Angelite for trade at Shiroku Pub.