This is the start of American Dub GX End Arc Bosses Arc. Cool title. First Yubel is here for her first win before the inevitable loss that will come. Sartorius is an okay duelist, but not at Yubel level. Yubel wins.
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Are we talking about Sartorius in his human/normal form or Light of Destruction Sartorius? The first one would lose badly, but Light of Destruction would demolish Yubel, actually he would demolish everyone ever excpet the chosen one (the one who can change destiny ) which is only Jaden. Jaden is the only one who can defeat Sartorius because he is his counter.
Sartorius definitely has access to his latter form here. It is immensely powerful, but so is Yubel’s final form and her special abilities. It’ll be tough for Sartorious to damage her and Yubel’s deck is also very powerful since she got many skilled cards like the new versions of the god cards.