Killer Machine (キラーマシーン Kirā Mashīn) are one of the four tribes from the Blue World.
Z/X Encyclopedia Entry
A group of murderous mecha controlled by renegade computers. Because the automated factories can mass-produce countless copies, they rely on tactics that allow them to run over their enemies with sheer numbers.
The obsession of the Killer Machine Factory Group's desire to massacre the Mermaid that fled to the ocean floor is infamous, but the use of electromagnetic waves in the ocean is limited, and the Mermaid nullify their amazing electrical attacks with the insulation technologies they've created, so they've had a pretty rough going. The offensive and defensive bombardments from both sides on the water's edge just keep on going.
In this way, traditional Killer Machine are assumed only to be able to handle dealing with normal humans. However, since the Black Points opened and they became aware of other worlds, new models were developed, such as anti-Giant, anti-Plant and anti-Spiritual based types. Depending on their use, their size and design can widely vary.