Club Zodiac

Club Zodiac is a club and a dungeon in the Persona 2 dualogy. It also acts as a hideout for the taiwanese mafia in Persona 2: Eternal Punishment. It should be noted that, in both games, a rumor can be spread to greatly change the dungeon's layout and add several items to the upper floors.

Persona 2: Eternal Punishment
The team heads towards the club in order to find out what's happening to the people who did the Joker curse who have supposedly been kidnapped. Upon entering, they meet Anna Yoshizaka. She says that the taiwanese mafia were the kidnappers, and that they could be found in the back of the club. The rumor to change the dungeon's layout can then be acquired by talking to a girl in the room.

Persona 2: Eternal Punishment

 * 2F: Spell/Media Card, Gun/S&W Magma, Item/Anti-Magic Bead, Item/Lucky Bag (x2), Spell/Frei card
 * 3F: Item/Battle Master, Spell/Suku Kaja Card

None of these items can be gotten if the rumor is not spread.

Resource
Treasure and enemy info for Eternal Punishment from FAQ/Walkthrough by Yushiro