Terrible Omen or T 666 is Primo's Duel Runner. Its Japanese name is written as T 666 (Ｔ・６６６), but the furigana characters indicate it is to be read as "Terrible Omen" (テリブル・オーメン, Teriburu Omen). 666 is the Number of the Beast from Christianity. The "T" designation may be taken from the Terminator franchise, where the titular machines are cyborgs like the Three Pure Nobles and are given designations in the style of "T-600", "T-800", and so forth.