How does the author know all this detail?
He doesn’t. However much of what what he wrote does make sense. Food for thought. It’s only when people pass off these speculations that go beyond what is clearly revealed in scripture that I get troubled.
He knows this because he’s an exorcist.
The Revelation granted to the Church in the forms of the Bible and Tradition.
Regarding Tradition, the Tradition handed down by the Fathers of the Church, and,
The liturgical Tradition handed down in the Rite of Exorcism;
The theological understanding of the angelic nature as understood from Scripture and developed by St. Thomas Aquinas.
The author's vast thesis research for his doctorate in theology;
The author's own experiences during exorcisms.
-Theo