I think they could do distortions. What would their bending philosophy be, though? Airbenders are all about evasion and finding their way around problems, earthbenders stand strong and face problems head-on, waterbenders are about redirection and changing the flow of battle to suit them, and firebenders prefer to strike first and strike hard. I can see lightbenders dealing in deception—creating illusions to baffle their opponents, tricking them into joining their side, etc. but I’m not sure what the inverse of that would be and how it would apply to shadow.

Honestly, I'm not an expert on combat mentality. I'm sure there are fitting themes that go well with both.

What about concepts that best represent each Element? Fire's Power, Air's Freedom, Water's Change, and Earth's Substance. I have an idea but I'd like to see yours first.

Well, shadows create hard lines, right? and if you can manipulate shadows, you can bring things to light that would be otherwise be in shadow (literally and figuratively). So maybe shadowbenders would focus on making things clear, especially since they don't like the show that lightbenders put on. I can't think of a word for that other than 'Clarity', which is kind of obvious and would show a combat style simple to the aggressive firebending, though I could see there being differences.

Here is what I think: I think for Light, it could be the Element of Progress. Now, I'll admit I had a discussion earlier with someone who described the "Element of Progress" for something else (Lightning. Yeah, I know weird). But, I think it fit Light better as Lightning is a Sub form of Fire.

For Shadow: I like thinking of it as the "Element of Mystery". Darkness conceals. Darkness is (mostly) unknowable. The People of Shadow would likely be (somewhat) enigmatic.

What about which culture these two would be based on?

Maybe India? The rest of the nations are based off of Asian cultures, and India’s pretty big. I would suggest Korea, since there are two, but… I’m not sure that would work. They could also be based off of the Middle East.

I think India works for the Lightbenders and I think Korea might work for the Shadowbenders.

I actually know some basic Korean martial arts, so that works out great!

Cool!

But would that really work? I mean, we've already established that lightbending and shadowbending are essentially the same kind of bending and that they're both the same people but just with different attitudes and morals and bending techniques (since shadows are the absence of light). Furthermore, Korean culture and Indian culture were based in two very different environments and their customs aren't really that similar. I think in order for that to work you'd have to change their culture a lot.

I think a better example would be India and a country in the southeast of Asia, like Vietnam or Thailand or Bangladesh (since they could have more root elements of the culture in common).