Right then, with the boss out of the way, it's time to hoover up the remaining loot in Brume Tower, and there should be plenty of it still glistening away in various chests, nooks and crannies. It's well-guarded in some cases, though, so avail yourself of our guide to avoid mishap.
Sweeping up loot in Brume Tower
Fast-travel or stomp your merry way to the Upper Floor bonfire in Brume Tower, then go towards the gated area (not the one up the small stairs) around the right corner and down the stairway. At the circular room, turn right. Here you can go three different ways via lifts. There's a Simpleton's Ring (making you invisible while rolling) if you take route 3B. There's loot including Titanite Shards and Flame Butterflies along route 3C. There's a chest with a Pilgrim's Spontoon weapon along route 3D. And 3E will bring you to a Baneful Bird Ring (reducing stamina loss while blocking with a shield).
Jump on the lift to the door above. It doesn't actually stop there, so you will have to hop off it while it's in motion. Go round the turn and descend the stairway to the room that had a chest at one end. Kill the two Possessed Armors, then pick up the Old Radiant Lifegem under the flaming statue. Go to the other side and out the doorway. On the balcony you'll find the Simpleton's Ring along the far right.
Use the lift to cross the small gap and get to the pathway on the other side of it. Open the door at the end and you'll be in a room with a few doors and a chest (containing Life Ring +3), which are being guarded by a Giant Club Demon whose health is continually replenished, meaning you can't kill it yet. The third door from the left leads to an Ashen Idol, so wait for the Demon to move away from there, open it and use a Smelter Wedge, giving you another Soul of Nadalia, Bride of Ash. Idol down, the Demon is no longer able to heal up. Kill him, then open the doors and the chest. You should end up with a Broadsword +7, 10 Titanite Shards, one Petrified Something and five Flame Butterfly items by the time you're done.
Take the lift to its lowest position and there should be a narrow ledge leading to an alcove. Step onto the ledge (jumping is not necessary) and you'll find a chest containing a Pilgrim's Spontoon weapon. Head back to the lift.
Go to the Throne Floor bonfire in Brume Tower. Go up the stairs, near the first Ashen Idol, then down the next flight of stairs. In the room ahead, go right and jump on the lift at the end of the ledge. Take it to the top and you'll find a Baneful Bird Ring in the vicinity of the railing. The ring cuts stamina loss while blocking with a shield - handy!
Right then, let's go find the optional Smelter Demon boss. Starting in the large round room beneath the Foyer bonfire, dig out your Tower Key to unlock the door near the lift that goes up. There's a big stairway ahead to go down, after which you should turn right and pocket a couple of Twilight Herbs. The lift on the other side of the platform brings you to the lower level and into the tunnel that leads to the Iron Passage.
If you're looking for page one of our Crown of the Old Iron King game guide then hopefully this link was helpful.