Bornogo's role in De Heptarchia Mystica is defined entirely by subordination: every prince in the system serves under the king who shares his day, and Bornogo serves under Bobogel, ruling Sunday under the Sun in the scheme's own day and planet correspondence. The manuscript, Sloane MS 3191, records the pairing from angelic sessions Dee conducted with Edward Kelley in 1582 and 1583, and Joseph H. Peterson's modern edition is the basis for what is known of the office today.
The Heptarchia's seven king and prince pairs form a complete week, each pair distinct from the next by day and planet alone, since the underlying office of 'prince' repeats identically across all seven: subordinate to the day's king, without the independent standing the Kings themselves are given in the text. That repetition is a feature of the source rather than a gap in the record: Dee's own material treats the office, not the individual, as the constant, and Bornogo's identity within it is carried almost entirely by the pairing with Bobogel and by Sunday's place in the week.
Because the Golden Dawn and the Enochian revival that followed it worked mainly from the Calls and the Aethyr Governors rather than from the Heptarchia, Bornogo has had a modest afterlife compared to those later figures, read chiefly by scholars of Dee's diaries and by the modern editions, Peterson's foremost among them, that finally brought Sloane MS 3191 out of manuscript.
Sources De Heptarchia Mystica (Sloane MS 3191), Joseph H. Peterson's editionJohn Dee, edited by Joseph H. Peterson with Arguing with Angels: Enochian Magic and Modern OccultureEgil Asprem