The Lost Books of Dionysius The Aeropagite.
“The Corpus is today composed of Divine Names (Περὶ θείων ὀνομάτων), Mystical Theology (Περὶ μυστικῆς θεολογίας), Celestial Hierarchy (Περὶ τῆς οὐρανίου ἱεραρχίας), Ecclesiastical Hierarchy (Περὶ τῆς ἐκκλησιαστικῆς ἱεραρχίας), and ten epistles.
Seven other works, namely Theological Outlines (Θεολογικαὶ ὑποτυπώσεις), Symbolic Theology (Συμβολικὴ θεολογία), On Angelic Properties and Orders (Περὶ ἀγγελικῶν ἰδιοτήτων καὶ τάξεων), On the Just and Divine Judgement (Περὶ δικαίου καὶ θείου δικαστηρίου), On the Soul (Περὶ ψυχῆς), On Intelligible and Sensible Beings, and On the Divine Hymns, are mentioned repeatedly by pseudo-Dionysius in his surviving works, and are presumed either to be lost or to be fictional works mentioned by the Areopagite as a literary device to give the impression to his sixth century readers of engaging with the surviving fragments of a much larger first century corpus of writings.”
(NB: From the entry on Dionysius the Aeropagite, or rather, Pseudo-Dionysius: The Aeropagus was an open air theater in Athens where lawyers or speakers declaimed in public. It was, in fact, basically a court, where eminent personalities could be addressed and pleas for clemency evaluated. There was actually an area where murderers could seek sanctuary from punishment.)
“Perhaps the most important Neoplatonic philosopher who influenced early esotericism during the Middle Ages was Denys the Aeropagite with his theory of a hierarchy of angels and of the universe. The Aeropagite’s worldview continued to be important during the Renaissance, especially for the angelic (or demonic) magic of Pico and Agrippa.”
—-Henrik Bogdan, Western Esotericism and Rituals of Initiation, 2007, pg. 53.