Guide:
The Mechanical Fundament is a set of tunnels, located underneath the Brass Fortress found in northern part of the Clockwork City. You’ll have to find a specific entrance, near the main market, at the center of the fort.
The Mechanical Fundament door is southwest from the Grand Depository. It is next to the path that takes you toward the western part of the fort. Once you get to the door, you’ll see the sign that you can enter this Mechanical Fundament.
Layers of layers, wheels within wheels: the Clockwork City has many levels, each with specific functions, often including adaptive instrumentality that enables the machinery to reach to change.
As you go inside the Mechanical Fundament, you should proceed toward the very end of the southeastern part of the tunnels. In this area, the light from the shard points to its location below. You’ll have to jump down in order to reach and collect the Mechanical Fundament Skyshard.