One Emperor and One Monk: I Will Kill You to Cross the Border

[No time travel, no system, mystical story, please don't enter if you mind] I kill, you cross. Thousands of years ago, there was a war between humans and gods, and the Immortal Emperor of the human race was in danger. The holy monk came to the rescue at the cost of his life, and both the emperor and the monk turned into souls and wandered for thousands of years. Ten thousand years later, the two souls coexisted in the mortal body of Xin Shi'an.