So, as soon as I got to Bloodstone, I went straight to the Hall of the Dead. But all I found in there was a locked door and a large fall. The large fall takes me to a path that leads to a treasure chest and... another locked door... and that's all I could find. I ran around for like 15 minutes and didn't find anything and ended up fast-travelling out. Anyway, anyone know what I missed in there?

That wasn't the hall of the dead. :)  What you found is called the "Sinkhole" and becomes available from the old pirate in the bar. Hall of the dead is a dive spot in the water off the docks in Bloodstone. Hope you see this before you go nuts. :)