Black Legion of Callisto

Part two of the series suffers from a lack of plausibility and a tendency to use dialogue as narrative. If you can overlook the faults (and if you watched the Disney Star Wars sequels you can tolerate anything) there is plenty of innocent enjoyment for fans of Edgar Rice Burroughs.

Having dispatched the Sky Pirates in Book 2 Jandar turns his attention to the Black Legion assisted by the pirates' seized flying galleons.
Structurally the Callisto series seems to be a rework of the Thongor series; compare the sequence of events as the hero encounters a disenfranchised princess right off the bat and later deals with various menaces one at a time as he builds a multi-city (and multi-species) empire. Some of the sloppiness of the Thongor series is avoided here though. For a start this series takes place over a brief span of time whereas Thongor's adventures happen over years.

Earthman Jonathan Dark, Jandar, on the Jovian moon of Thanator, infiltrates the barbaric Black Legion, a mercenary army controlling Shondakor, to rescue Princess Darloona from a forced marriage. He sabotages the Legion from within and helps the city reclaim its freedom.

Jandar aids the Ku Thad people in an uprising, defeating the Legion, but the villainous Prince Thuton escapes with the Princess.