A Mechataur's body is made entirely of metals in shades of gray and brown. It has glowing eyes ranging from green to yellow to red, a bull's head, and horns each having three sections. Inside its torso, covered in brown plating with gold accents, is a compartment for its core, which turns off and on depending on the Mechataur's power setting, sealed with a grilled cover; should the core turn off, so will its eyes. Its arms are partially armored, exposing some wires and gears inside.
The Mechataurs are designed as the protectors of the Foundry's labyrinth, and as such are designed for combat; as shown in Book 1, Chapter 13, at least two are stationed inside the maze. They can overwhelm multiple opponents, even those with a weapon, using their sheer bulldozing force and powerful punches. Only those who can figure out their intentionally-programmed weakness can defeat one.
The machine's eyes are indicative of its mood: yellow for standby, green for friendly, and red for angry. The one Kenna fought against seems to be an imperfect creation while inside the labyrinth, as Whitlock had difficulty perfectly recalibrating it to distinguish friend from foe after it was recruited, seen in Book ,1 Chapter 15 when it almost punched the queen during her seige of Stormholt.
Whitlock created the Mechataurs specifically as guardians in the Foundry's labyrinth. He later reprogrammed one for use in more conventional battles. Since the Mechataur used conventional means of fighting, Whitlock didn't see a problem with the construct being used as a weapon, since it was essentially a repairable soldier.
In Book 1, Chapter 14, during his expulsion of Hex from the Foundry, Whitlock managed to summon the machine to his defense, indicating that he also used it as his bodyguard while inside the city; whether this copy was either one of the two inside the labyrinth or a third creation is unknown.