World Breaker

The was a weapon of mass destruction created by the Jiralhanae Kingdoms, under the orders of Emperor Marius. Designed by the scientist, Malchus, it was utilised against the enemies of the Kingdoms, laying waste to whole cities, and leading the subjugation of dozens of worlds. 
The World Breaker was created in the months following the Kingdom's victory during the blockade of Te. With the Lekgolo homeworld conquered, and the Lekgolo now subjects of the ever growing Jiralhanae domain, they were utilised to not only begin harvest the materials for the construction, but to become part of the war machine itself. Millions of worms were herded into its construction, bonded into it to function as a living motor for the machine. 
The World Breaker is a six legged war machine, weighing in at 180 metres tall, 227 metres wide, and 380 metres long. It has incredibly heavy all round armour, and starship grade energy shielding. It features massed batteries of cannons, including heavy plasma cannons, bombardment guns, banks of point defence weapons, and a single energy projector for bombardment along the front spire. It has a highly accurate point defence system using A.I. guided pulse lasers to cut down incoming ordnance. The armoured front protects the more vulnerable rear, which consists of two booms containing hangars and launch decks, allowing it to play host to dropships, fighters and gunships. Slung under its belly is a gravity lift, allowing it to deploy armour and soldiers directly to the ground. At it's core, it is hooked up to a salvaged Forerunner power core, a device intended to power a warship, but repurposed here to power this war machine. This core powers the shielding and weapon, and it also powers the boosted gravity propulsion drive that vastly reduces the weight of the war machine, and stops it collapsing under it;s own weight.
The entire machine is controlled by an entity called the Witch. The tortured remnants of a captured human A.I., she is shackled to the machine, and controls it with a an uncanny precision, and a twitching, screeching fury.