Cryptic crossword No 3,335

My first attempt at a themed puzzle. Many thanks to those who've solved and commented on my previous efforts, particularly Someguyinthefridge for his in-depth analysis. Hope you all enjoy.

Thanks Cricket, I enjoyed the theme (once!) and most of the clues too. Had a lol with 18d and ticks for 3a, 7a, 12a, 1d, 5d, & 6d. Great to see you improving your technique. Just a couple of issues below…

Sisyphus picked up most of the points I was going to highlight. 12a Ares (god of war) isn't the same as Aries (zodiac sign). 14a needs a question mark to indicate the solver needs to think of an -example- of a prince (without this, you're telling them to find a -synonym-. 20a requires the solver to insert a substitution into an anagram, but you haven't justified that. 3d - I don't think the definition is sound. 17d is missing a definition entirely.