NOTE: For this achievement, you need to have already collected the hammer and possibly something heavy from earlier in the game.
No other tools will be needed from before this area.
The area you can find this is in Flashpoint Caves I. This is after you have passed a floating orb emanating a green light that is scanning for life. If it sees you, it will shoot beams of red light that cause electrocution damage. When following the cable to find the power source, you will get to a point where you find the Forward Vector point.
There will be a key nearby where the cable leads upwards and you will be told to find a path upwards. You can go four different directions: back the way you came, right, left, or straight.
Go to the left door and use the key. Be wary of traps that fall from the ceiling. They are explosive. At the end of the short tunnel, on the left will be a tablet with a key at its base. Pick up the key, then go behind the tablet.
The wall behind the tablet is breakable. This is where the hammer comes into play. Hit the wall eight times, then go into the now opened chamber. There will be a sword on the ground
Pick it up.
Exit the tunnel and when you get back to the intersection, go left (or what was the straight ahead path). You will know it because there is also a campsite area with water, food, and a skeleton.
Use the key to open this door. As you enter, be wary of traps again. At the back this chamber is another breakable wall. Before breaking the wall, there is a stone setting on a stool/stone seat. Pick it up.
Once the wall is broken, head forward to the rear of this chamber and push the block with the gear forward until you can squeeze by it into yet another chamber.
In the middle of this room, there is a pedestal with three gears atop it. You may have seen mechanisms like this in the game earlier. The sword goes here. Once the sword is in place, activate it to open a door to
another chamber!Upon entering this room, there is a pressure plate. This pressure plate requires something heavy to be placed upon it so the door will stay open.
When the door opens, it reveals a room that is filled with a bubbling liquid. Wilson will warn you it is toxic. Jump in and the achievement is yours.