Killer Twins appear on the lower floors of the Yabbashah Block within Tartarus. They will boost with Mind Charge before using their Zionga skill. They will later appear in the first section of Antenora within the Abyss of Time. This variant will attempt to Enrage the party to inflict more damage.
Killer Twins appear in halls 9 and 10 of the Steamy Bathhouse within the Midnight Channel in normal encounters and possibly earlier as Red Shadows. They well generally use their Physical attack skills or try to cover their weakness with Red Wall so that it cannot be exploited. Upon being defeated, they may drop the Gray Shackle material. Selling 6 Gray Shackles at Daidara will unlock the Santou weapon for Yosuke Hanamura.