As a Catholic you should know this:
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.
The Bible is not the sole rule of faith and morals for the Church. Revelation is a larger body and the personal experience of the exorcist must not be discounted.
-Theo
Oh! St Thomas wrote about it. It was said He had literal visions of St Paul and St. Peter too.