Iron Keep (2 of 3)
When you enter the second area of Iron Keep (with all the walkways), make an immediate left to find a contraption along the wall. Use a lockstone to reveal a fake blue wall. Bust through to find a ladder to a chest containing a Thunder Quartz Ring +1. This also opens the passageway to Belfry Sol.
Iron Keep (3 of 3)
To get this, first head to the second section of Iron Keep (with the walkways and greatbow-wielders). Take the ladder in the back, then follow the stairs to a second ladder. This leads you to another Pharros' Contraption. Like the first one in the area, this creates a pool of water you can use to temporarily boost your fire resistance.
Grave of Saints
Most of the Pharros' Contraptions found on the path to the Grave Entrance bonfire are meant for the Rat King covenant; they merely activate traps. Only the two directly across from bridges are useful to you right now. They lower their respective bridges, giving you access to a room where you'll find a corpse holding the Whisper of Despair hex.
Shrine of Amana
This is just across the water from the Crumbled Ruins bonfire. Place a lockstone reveal a fake blue wall. Bust through to find a chest containing the Helix Halberd.
This is found in the room where you drop into, and bells ring. Look for a spot on the wall with no bevel; interact with this to reveal a fake wall. Behind this is a Pharros' Contraption. Use a lockstone to reveal another fake, blue wall. Smash through to find a chest containing Oleford's Staff and the Great Lightning Spear miracle.
After heading up the stairs to the top floor, you'll find a pull-chain on a dragon statue. Pull it to open the next room, head inside, and make an immediate right. There's a contraption along the wall here. Use a lockstone to light the torches in the hall, making the area a little easier to navigate.
Just up the slope near the Shrine Entrance bonfire is this archway; head underneath to find a contraption. Use a lockstone to reveal a fake blue wall, then bust through to find a chest containing the Staff of Wisdom and Judgment Armor (Full Set).
Memory of Orro
You'll find this inside the Memory of Orro, accessed by using the Ashen Mist Heart on the fallen giant beyond the Pursuer boss area. Inside, take the left path up to find a room with ballistas and Hollow Soldiers. You'll find a contraption here too. Use a lockstone to reveal a fake blue wall, then bust through to find a second contraption and chest. The rigged chest contains a soul, and the other contraption is a trap. You'll also find a fake wall in here that allows you to obtain the Steel Armor (Full Set).