Within De Heptarchia Mystica, Babalel is one member of a fixed sevenfold structure rather than an independent figure: a King ruling one day of the week, paired with a subordinate Prince who serves under him rather than ruling in his own right. Babalel governs Tuesday, correspondingly assigned to Mars under the system's own day and planet scheme, and is recorded as paired with the prince Befafes.
Assigning a ruling spirit to each day of the week, and pairing that day with a planet, was not a convention Dee invented. Renaissance ceremonial magic already had grimoires that organized angelic or planetary intelligences by day, the Heptameron long attributed to Pietro d'Abano among them, so Babalel's position in Dee's scheme belongs to a wider genre of period magic rather than to a system built from nothing. What distinguishes the Heptarchia within that genre is its source: not a printed grimoire compiled from older material, but a record Dee kept of what he understood the angels themselves to have dictated through Kelley in 1582 and 1583.
Because the Heptarchia was never absorbed into the Golden Dawn's later Enochian curriculum, which drew on the Calls and the Watchtower tablets instead, Babalel has been read mainly by scholars of Dee's own diaries rather than by twentieth century ceremonial magicians, and the office Babalel holds is best understood as part of Dee's own working system rather than as a figure later orders re-used.
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