Back when I was first getting into the OSR, Dark Dungeons was one of the early retroclones that I stumbled upon. Back in those days, I was grabbing up every free or PWYW PDF that I could. I was on a search for a set of rules that spoke to my inner youthful grognard.
Dark Dungeons is a stand alone game and has the usual classes and race-as-class. It draws it’s inspiration from the Rules Cyclopedia and BECMI. Heck the character levels go up to 36. That’s right 36. I don’t know anybody who normally plays at such levels but you can do what you want.
Because there’s so many retroclones, nobody really has the time to play them all. So like some of the others, Dark Dungeons is one of those that sits on hard drive as a reference work. As I said, it’s a complete game. So not only does it have all the rules and stuff that you would expect, it also has rules for some that are missing from other games. like strongholds and domains, aerial combat (including sky ships), naval combat, mass combat (War!), extra-planar adventuring, and having PC’s become “Immortals”. While you may not use all of these components in your game, it is nice to have them readily at hand when you’re designing your campaign and don’t want just another cookie cutter setting that doesn’t have anything odd in it.
You can grab the original edition of Dark Dungeons or the 10th Anniversary Edition on DrivethruRPG for PWYW. You can also find out more about the Dark Dungeons and other of their games at the Gurbintroll Games website.