Garmatron

The Garmatron is the ultimate weapon created by the Overlord and his Stone Army. It is a large tank armed with an oversized cannon that can fire enormous projectiles filled with Dark Matter.

History
When Lord Garmadon first met the Overlord, the latter promised him an undefeatable weapon of colossal power. The Stone Army began mining Dark Matter for the weapon's construction; later, the Overlord stated that when the Celestial Clock completed its countdown, the ultimate weapon would be complete.

In Return of the Overlord, the Garmatron is finally completed, and Lord Garmadon pilots it to the coast of the Island of Darkness. From there, he uses the Garmatron's cannon to launch Dark Matter missiles at Ninjago, infecting parts of the land with darkness. After a few shots, the balance between light and darkness in the world is upset, allowing the Overlord to possess Garmadon's body.

In order to increase his power further, the Overlord aims the Garmatron's next projectile at Ninjago City, but the Ninja attack the Stone Army to prevent them from loading another Dark Matter missile. General Cosu attempts to stop them, but Sensei Wu kicks him into the Garmatron's loading bay, causing the Overlord to mistakenly fire his subordinate into Ninjago City. After a fight with Lloyd, the Overlord decides to attack Ninjago City directly, opening a portal and leaving with the Stone Army and an infected Nya.

Abilities
The Garmatron is massive and powerful, able to crush or push aside anything in its path - despite this, it can also move fairly quickly for its size. Its armaments include movable spikes between its treads, small turrets on either side of its hull, and its main cannon, which can fire projectiles clear across the Endless Ocean. Its usual ammunition is a large missile with a Dark Matter warhead, allowing it to infect large portions of land with pure evil energy. The cockpit - located at the top of the machine - features a lever-activated trapdoor in the middle of the floor, allowing the pilot to drop enemies into a internal bay and then catapult them out of the Garmatron.

Although the Garmatron has not displayed any structural weaknesses, its weaponry has a few exploitable flaws. Its side turrets can be commandeered by enemies (as Kai did) and turned against the Overlord's own forces, its main cannon has a twenty-second warmup period before it can fire a shot, and its Dark Matter ammunition must be loaded manually into a port on its side.