For Cody
The Depths is an area all the way at the end of a long maze through mines and tunnels. Really, you just have to navigate the the Fogstone tunnels until you reach the depths. It's a serious trek, and it will take a while. Especially since you will have to dodge tons of automatons. Unless you have a friend of course. If you have a friend you can fight the automatons. If you didn't know yet, you enter the fogstone mines or tunnels or whatever they're called through the Lagoon. I really can't tell you how to navigate the tunnels, because I'm not that familiar with myself either. When you reach the depths, there is a chest in a far corner of the area. Somewhere around that area will be a Bigfoot Automaton. (I think it's invisible.) Fight it with a friend and get the key to open the chest. Inside will be plans for the Cog Sword.
There is also another way to get the plans for the sword.
Somewhere down in the mines is the Fogstone Caverns. There's a chest and a Bigfoot all the way at the bottom of the Caverns. Someone told me that the Fogstone Caverns chest contains the same plans as the Depths chest. So it doesn't matter which one you decide to open. The second chest will be empty. I'll be getting on soon, and I can help you if you like.
etherdood