From this article I’ve found that:
1. Kishimonjin represents the ninth consciousness permeating all the other consciouness.
2. Kishimonjin represents turning demons into benevolent forces.

Ikeda: The Mother of Demon Children, who dotes lovingly on her own children while not being the least concerned about the children of others, symbolizes the negative side of the maternal instinct. By contrast, to take the love one feels for one's own children and extend it into a love of humanity is the spirit of the merciful mother Perceiver of the World's Sounds, of a bodhisattva.

The Daishonin explains that the name of the "evil demon" Mother of Demon Children can also be read in reverse: "The word jin or 'Goddess' represents the ninth consciousness. The word mo or 'Mother' represents the eighth consciousness, the level at which ignorance appears. The word shi or 'Children' represents the seventh and sixth consciousnesses. The word ki or 'Demon' represents the first five consciousnesses, those of sight, hearing, smell, taste, and touch" (Gosho Zenshu, p. 778).

Simply put, the ninth consciousness is the world of Buddhahood. When the world of Buddhahood in the depths of our life wells forth, the eighth (or alaya) consciousness changes, as does the seventh (mano), the sixth (which corresponds to "mind"), and the rest of the five consciousnesses. These are all purified and come to function positively.

Through the power of the Mystic Law, the Mother of Demon Children becomes a benevolent demon. When we have the strong faith to fight resolutely for kosen-rufu, then even evil demons turn into benevolent forces. Our obstacles become our aids.