Superheavy assault tank.
Grizzly tanks are armed with dual high-velocity cannons that make quick work of most armored vehicles and dual medium machine guns to suppress enemy infantry. The missile barrage upgrade allows them to fire an area-of-effect bombardment. The Grizzly's heavy armor is reflected in their slow speed and cost, and they are vulnerable to enemy aircraft.
Approaching the upper limit of mass and volume that can be dropship-transported, the Grizzly is a superheavy tank unit deployed as a siegebreaker by specialized UNSC armored groups. The Spirit of Fire has an unusually large complement of the vehicles due to the machinations of Sergeant John Forge, though the secrets and convoluted story of their acquisition went with him to the grave.