Ke Mo was a general from the Banyue Kingdom. He's best known for being one of Ban Yue's earliest and most loyal supporters—he played a crucial role in helping her rise to the position of Imperial Preceptor. But things fell apart between them later on. When Ban Yue made the decision to let the Yong'an army into Banyue, Ke Mo turned against her. By that point, the kingdom was already on its way down, and that move apparently felt like a betrayal he couldn't forgive.
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