• Designated Hero: The Kondalians have practically no traits that would be considered sympathetic by modern readers. They have no concept of democracy, race-based slavery is unquestioned, they've been at war for 6000 years over ideology, are Social Darwinists who believe themselves a Superior Species, and admit to having no concept of mercy. All in all, they are no better than the Mardonalians; the only reason they are considered good is because they were nice to the heroes.
    • Unlike the Mardonalians, and the villains generally in the series, the Kondalians are not Absolute Xenophobes, but willing to co-operate peacefully with other planets. That said, they are typically portrayed as a species of Proud Warrior Race Guys, with a strong whiff of Barsoom. They're very flawed good guys, and they do occasionally get called out on their warmongering by the human protagonists.
    • The series ends with the Crown Prince of Kondal essentially admitting 'We are complete barbarians by the standards of the civilized galaxy and we're going to have to change, or else we'll be left behind.'
  • Magnificent Bastard: DuQuesne.
  • Older Than They Think: A "dark star", essentially a black hole, and mushroom clouds produced by the atomic/total conversion of explosive shells. Both in The Skylark of Space, published in 1928.
    • Early drafts are said to go all the way back to 1916. That is sixty years before Star Wars.