Stone Tooth was the second great digging machine, built by the D'ni in 5359 DE. It was more powerful and technologically advanced than its predecessor, Stone Eater. It is described as being almost mantis-like in its appearance, with jaws that bit away at the rock face, pouring debris through vents in its segmented underbelly into hopper cars ready to transport the material away from the work site. By the time it was used to help construct the Great Shaft, the machine was over 4,000 years old, earning it the moniker "Old Stone Tooth".
As the oldest digging machine still in operation at the fall of D'ni, Stone Tooth was used in many excavation and construction projects over the centuries. The following is an incomplete list, built up primarily from DRC research materials. Dates indicate the beginning of each project.
- 5359 DE: Uran District initial excavation
- 5714 DE: Tunnel from the City Proper to Ae'gura (incomplete, cancelled)
- 5374 DE: Lanaren District initial excavation
- 5856 DE: Exploratory tunnel excavation
- 6430 DE: City expansion under King Jaron
- 6601 DE: Expansion of the City Proper under King Rikooth
- 7539 DE: Opening of the Tijali Mines
- 9336 DE: Construction of the Great Shaft