Mantoids are robots made by Aku's evil scientists after the X-Models and the Beetle Drones. Like the Beetle drones, they serve as enforcers of Aku's will on the ground. Like their name implies, they resemble a praying mantis. They are voiced by Phil LaMarr.
3 Mantoids were pursuing Jack intent on destroying him. Upon being lead to the secret construction site of a group of human scientists attempting to construct a space shuttle to escape Earth, they turned their attention away from Jack to alert the scientists that their facility was in violation of Aku law and that they will all be killed. Before they could do too much damage, Jack attacked the Mantoids and destroyed 2 of them. He attempted to destroy the third and final one, but upon decapitating it, its head used rockets to retreat. It would later alert Aku of the facility's location, resulting in a larger group of Mantoids being deployed to insure the destruction of the facility and the humans using it. They arrived at the location the following morning, but the rocket immediately launched, leaving the Mantoids unable to fulfill their objective.
They were presumably erased from existence after the past Aku's destruction.