Iron Passage

A timed gauntlet of cells leading to a second, magic-wielding Smelter Demon.

Bosses

Blue Smelter Demon: Same moves as the Iron Keep Smelter Demon but with magic damage; bring magic defence.

Pharros Mask (Crown of the Old Iron King): On a corpse past the Aged Smelter Demon's arena in Iron Passage.
Smelter Demon Soul (Crown of the Old Iron King): Defeat the blue Smelter Demon at the end of the Iron Passage.

From Foyer ride the lift down and use the Tower Key; grab a Twilight Herb, ride down and light Iron Hallway Entrance
Summon Drifter Swordsman Aidel and Steel-willed Lorrie here only after the first route, since they cannot follow your rush
Pull the lever to free the Ashen Warriors and grab the Large Titanite Shards; the timed gate shuts, so reset at the bonfire and rush through next time
Kill the Astrologist, go left through the hole without dropping and take the Crimson Water
The other lever's cells hold Simpleton's Spice and Torches
On the right path drop down, kill the Possessed Armor and loot Old Growth Balms and Cracked Red Eye Orbs; a ledge below has a Dried Root
Take the left path along the upper ledge for Wilted Dusk Herbs and reach the fog
Defeat the Blue Smelter Demon; same moves as the Iron Keep one but with magic damage. Reward: Smelter Demon Soul and 75,000 souls
Through the tunnel a corpse has the Pharros Mask; ride the lift back to the bonfire