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BBB (ビィビィビィ, Byibyibyi?) is an "invincible anti-Servant robot of annihilation" created from old arenas of the Moon Cell Holy Grail War. She is an "unparalleled" mech-sized Labyrinth Robot guarding the third floor of the Sakura Labyrinth. In creating her, BB spent two minutes going to the Near Side, collected parts and pieces of old arenas, disassembled them into an enemy program, reset it, and then programmed her own "superior thought routines" with lots of surplus memory. BBB was programmed not to leave the third floor, but Passionlip used Trash & Crush to crush her and throw her into the arena.
BBB is described by Passionlip as "self-important and uncute", and it is said she is more honest about her feelings than BB.
BBB was planned to appear in the third chapter, but was scrapped due to not being an interesting boss.
This tag implicates bb_(fate) (learn more).