The main part of the expansion takes place in the Brume Tower, a huge intricate pillar that you must descend to find the boss. This area is more reminiscent of the first Dark Souls in design, rewarding you with unlockable shortcuts and new ways to explore areas you thought you'd already cleared. This is great - since the DLC focuses on just the one tower, you feel as though you're conquering the place and learning its secrets, rather than just blowing through a dungeon.
In the first DLC I was struck by the upgrades to enemy AI, but I didn't feel it as much here. Some tough fights can be manipulated into relatively trivial affairs if you play it right. Well, except for one particular invasion, where the phantom fights for a bit and then runs down into a curse-infested tower protected by respawning enemies. What a jerk. If you know your items there's a way to turn the tables, but I won't spoil it for you here.
One thing I liked and didn't like at the same time is that one of the bosses is extremely challenging if you don't fully explore and/or conserve resources on your way down. Four idols outside the arena heal him when he gets within range, so if you want a fair fight you'd better find the way to destroy the idols.
The optional area, the Iron Passage, looks really cool - it's pretty much made of iron ore - and gives you a choice on how to approach the area. But there's only one bonfire, so making it to the boss alive can be quite troublesome. The astronomers are fairly smart, mobile casters, and the sorcerers will teleport and try to backstab you. Those are neat, but the possessed armours and hollows can be maddening. And the finale to this area I spent so much time grinding through is... the Smelter Demon again? That's kinda lame.
After Smelty, I remembered I'd found an area with an armour stand that looked like it did something but I couldn't access. I figured maybe it would do something now that I had the crown, so I went back and the armour was glowing, but still didn't do anything. Turns out you need both the crown and the seed of a tree of giants, because it's a memory you can access. This annoyed me a bit because I'd started a NG+ playthrough and haven't re-acquired the seed yet, so I've got to progress the campaign even further before I can finish the DLC. This is why I delayed this write-up for so long: I figured I'd just play through the game more to access the final part of the DLC, but I got bored of that and stopped. I waited long enough that I figured I should just publish the damn article.