I can be a helpful Hârniac.I keep seeing this one getting mentioned over the years, but I've never really picked up on why it's so popular. If it's what I'm after, I'm certainly willing to give it a look. On that website, though, I wasn't able to find anything that looked like a surface-level introduction.
Here's an intro:
Don’t know anything about Hârn, or HârnWorld? This is an introduction and teaser for the setting.
Here's a publisher of Hârn material:
And the ever-friendly Hârn Forum:
With regards to Thedas, I'm not an authority on the setting (I just think it's cool), so I'll leave that to others.