Furious Gigas is a sub-boss, found on the 72nd floor of Tartarus in a group of three. They impede the party's progress and must be fought in order to continue. They are later encountered as normal enemies on the Yabbashah Block of Tartarus, between floors 99 to 113.
They may later be found in the first section of Caina within the Abyss of Time.
Furious Gigas appears in B3F and B4F of the Secret Laboratory within the Midnight Channel. They will use Rebellion to increase their Critical Rate before attacking. After being defeated, they may drop the Proof of Passion material. Selling 6 Proof of Passion materials will unlock the Divine Blouse female armor in the shop.