M510 Mammoth Mobile Anti-Aircraft Weapons Platform Siegework/Ultra-Heavy

The , known as the Mammoth, is one of the largest land vehicles in use by the UNSC. It is a multi-purpose platform, for targeting enemy aircraft, star ships, and terrestrial fortifications. As well as this, it has all the facilities to operate as a mobile base of operations. 
Deployed either as a mobile planetary defence system, or as an expeditionary vehicle, the Mammoth packs a surprising amount of versatility. While its size limits deployment and accessibility, it has enough speed, armour, and bulk to carve its own path through otherwise impassable terrain. The main gun of the Mammoth is a Mark 2457/35cm HRG, a heavy duty MAC capable of performing a number of roles. It can act as orbital defence, targeting suborbital ships and installations with good accuracy, firing slugs capable of demolishing light targets, and damaging heavier ones. It can also target aircraft, either in atmosphere, or in suborbital positions. This cannon can also be loaded with munitions intended to be used against static terrestrial targets, allowing it to act as an artillery piece, firing at lower power against strongholds and fortifications, being accurate at massive distances. In accordance to its anti-air role, it originally carried two non-static rocket pods, but these have been replaced by independent anti-air turrets, taken from the M820B2 Wolf Spider Air Defence System. This uses four 40mm cannons, and two missile pods carrying four Slamdunk anti-air missiles, capable of targeting a variety of air targets, and even being turned against ground targets. 
As part of its complement, its internal pay carries space for three Warthogs, and 20-30 personnel. These are usually defensive details, carrying fire control systems, or defensive weapons, intended to protect the vehicle, and establish perimeters. They can also be an extension of the expeditionary role, carrying necessary gear to perform short ranged operations, or deploying into combat. The internal bays carry magnetic clamps to lift Warthogs, increasing storage space and giving space to repair damaged vehicles. It also includes weapon and ammunition stows, and a large command room containing fire control systems, orbital communication relays, and command systems. For loading and unlocking, it has two side ports, and a front and rear ramp, as well as external roof access and parapets. 
The Mammoth is covered in heavy duty armour plating allowing it to sustain significant harm, and onboard carries three fusion power plants, one powering the gun, and two used to operate the vehicle's motors and internal systems. It has six massive all terrain vehicles, each with their own variable steering.