Am I missing something? (Swamp)

After beating the Elder I have been carefully venturing into the Swamp. The only thing is, I get the feeling I'm missing something.

I've fought Draugr villages, leeches, slimes (and oozers), skeletons, a wraith, and a couple abominations (by Odin, what nightmare fuel. Thank goodness there were trolls I could use to lure to them).

Two corpse piles next to a bone pit were a nasty surprise. There's an odd statue or two, and a couple of areas with Runestones on the Draugr with the bricks.

I feel like I'm missing a resource/Dungeon. I know there's a boss somewhere. I've gotten the Root from the Abominations, guck off a tree(not sure how to get the ones not ground level), turnips (not done growing; trolls killed my first crop the villains!), and even a Chain from a Wraith. Hell, I even snagged a few black metal scraps off some Fulings and a couple needles from Deathsquitos in a tiny Plains segment I found.

And yet, I haven't found anything like Copper or Surtling Cores, or another wood type that really gives you access to another suite of upgrades and buildings.

Am I just missing something (if possible without spoilers. I love the discovery in this game)? I've been through a large stretch of a swamp area too

The Draugr stone said to bury them. Is this a hint? Should I bring a pickaxe and dig? Or do I keep searching?

Edit: I have the Elder key but have been leaving it home due to not wanting to drop it when I die. Assumed I would find it and then go fetch the key. Inventory is a premium too.

Thank you all!! I'll keep searching. Still more mysteries in the swamp to find I see from what you're all saying.