The unofficially named Robotic Guard is a creation of the Dwarfs, which Mari notices its mechanical like abilities. They appear in Hammer's Reach (as a Mini Boss), Under Hammer (as a Defender in a cutscene), and Thunder Hammer. Their role is to defend the dwarf territories.
There are two types: the Spiderbot Guard, and Mecha Taurus. Their body structures are the same, but they have different heads.
The Guard seems to have three attacks. One is where it will shoot a (fixed) machine gun on where the target last stood, another is where it can shoot a laser similar to the Siren's Oracle, and it can throw off multiple bombs to its side.
The prime differences between the Spiderbot Guard and the Mecha Taurus is that the Spiderbot Guard can shoot out four bombs simultaneously, while the Mecha Taurus only shoots two. The laser of the Spiderbot also adds additional explosives as well.