The Light Brigade, known in Japan as the Four Monarchs (四帝, Yon Tei), is a group of assassin duelists in Sarina's service. All four Members decks are centered around a "Monarch". In addition, each member of the Light Brigade possesses some sort of element-based power. Frost, Thunder, T-Bone and Blaze are shown to travel through snow, lightning, earth and fire, respectively; and the four seem to be responsible for using the Duel Spirits of the Monarch cards to create a spiritual barrier around Domino City.
The Light Brigade is introduced as Duel Academy students go on a field trip to Domino City. There, Frost and Thunder duel and Tyranno Hassleberry and Syrus Truesdale, Frost defeating and kidnapping the two after eliminating them and Thunder at the same time. T-Bone later duels Jaden Yuki and loses.