Central Bonfire
Continue to the next room and light up the bonfire. There are now two paths here; the stairs going up leads to blocked gate, with several Alonne Knight archers sniping you at a distance and a heavy knight waiting upstairs. Take the stairs going down instead.
You'll reach an inoperable lift so ignore that and take the long ladder up instead. Once you've reached the top, you'll be in a room where several stone statues come to life. You can open the door immediately and head there to filter out the enemies and to avoid accidentally triggering the other statues to revive. This room also has two chests that contain an Old Knight Hammer, and Caitha's Chime and Soul Greatsword.
You can kill at least spearman enemy near the golem to use its soul and make the golem come alive, lowering the lift outside the Central Bonfire.
Head to the next hallway where you'll find more enemies. Be careful of the Alonne archer knights on the balcony. You can run upstairs and kill the Alonne Knight archers. If you can deal powerful ranged attacks, it will be better to stand beside the columns to avoid getting sniped by the archers in the balcony across. Kill the two Alonne knights to the left and you'll get a Firestorm spell from the chest. The chest in the other balcony just contains rubbish so you can just ignore it. The two knights guarding the doorway will stand by their position and cannot be lured. You can however, lure the Mastodon warrior and deal with it using ranged attacks.
Open the door ahead and kill the Mastodon Warrior. Go downstairs and open the door to reach the armory. Loot the corpse beside the stairs to get Repair Powder x5 and Flame Butterfly x10. Open the chest to get an Estus Flask Shard. Now pull the lever to open the iron gate blocking the door, leading back to the central bonfire. Backtrack and rest then step on the lift. (In case you stepped on it accidentally and it ascended without you, you can use the lever now to call it back down)
There are a lot of chests here where you can loot Strong Magic Shield, Soul Vessel and Fire Seed, and Key to King's Passage. Ignore the Embedded since you'll need to stab it using the Key to the Embedded item that is dropped by the Demon of Song. Ignore it for now and take the lift down. Use the key to open the heavy iron gate leading to the King's Passage.
The chest on the opposite side of the Firestorm chest does not contain rubbish. It contains 10x Fire Greatarrows. Be careful though, the chest has an arrow trap when you open it.