Broken Bot

An alien ship has taken possession of multiple cities on planet earth, deploying countless robots that no weapon created can destroy. After the failure of the attack, humans have been relegated to an underground world and scientists have built secret laboratories, and developed their first prototype of the Leviathan project, an exoskeleton made up of robots and dinosaur head with lethal jaws and brute force. There are portals scattered around places where robots can be transported from one place to another making it hard to locate but once encountered a single discharge of Leviathan weapon can blow them into pieces.