After recalling Mundus's previous actions, even Dante and the others had to admit that what Bayonetta said was probably true. Balder was deceiving Mundus.
Mundus had plundered the marks of other demons, and under the power of the marks, his soul became immortal. Perhaps in his understanding, this was one of the prerequisites for a demon lord to promote to demon king. He thought that what he lacked next was only power and authority, but he did not realize that this mark was only half a divine spark.
Balder might have told Mundus that he would help him become a demon king, but he had concealed the information about the other half of the mark from him. His true goal was to take Mundus's already solidified mark.
