This is an LXQt theme version of my favorite dark theme ever, Leech for GTK2.
Leech is the theme I fell in love with just days after installing Linux for the first time, waaaaay back in 2004. To this day I still use it whenever possible. However, there's no comparable GTK3 theme, and as it looks like Qt and Qt-derived desktops are the wave of the future, I decided to port Leech to LXQt's .qss stylesheet format.
This isn't a completely accurate port, as the original had some subtle gradient effects I can't quite figure out on the buttons, but it's very close and may even look just a tiny bit cleaner. It works well alongside the real thing, which is the important part.