Gatebreaker Mega Gargant
Gatebreakers have only contempt for the cities and strongholds of civilized races. Nothing entertains a gatebreaker more than shouldering through a castle wall in a massive blast of brick dust, collapsing hundreds of tons of masonry at those hiding behind it and killing those occupying the walls fall.
The Gatebreakers are the most merciless and ferocious of all Mega-Gargants. These are walking siege engines that thrive on smashing their way through city walls, those fake havens built by little fry who think a fancy stack of bricks will protect them. Some have even been known to smash the skull-encrusted walls of a dreadhold to rubble, or smash their heads down on the spiers and citadels of these architectural marvels built by the elven race, proving that even these mighty edifices were built with enough brute force and ignorance can be thrown into the dirt.
The motives that lead gatebreakers to attack the settlements of the Mortal Realms are threefold. First, they know they are native to areas where Sigmar's new civilizations have begun to take root, that the cities have good food - some are even smart enough to raid a new metropolitan area rather than destroy it, and leaving enough of it intact for it to recover and gather more defenders to make it a more attractive target for the next attack. Second, they are driven by the need to show their superiority to the upstarts who think they can claim the land for themselves. Finally, and perhaps deepest, they hold a grudge against civilized guys that can never really be settled
At a deep ancestral level, these Mega-Gargants know that it was the forces of civilization that slew their ancestor Behemat, just as Sigmar the God-King slew Ymnog in his turn. They would happily kill the God-King if they could, but realize they don't have enough power to bring him down - not yet, anyway. They are content to destroy the stormkeeps and commanded districts that human types go to such pains to build.
Their claims of destruction aren't useless, of course, and are usually backed up by the trappings they take with them on any warpath. While a rural gargant wears the pelts and skulls of the great beasts he slays, the more urban gatebreakers scoop their trophies from the cities they love to destroy. Temple bells still attached to oak beams, precious standards that once flew from palace spiers, tavern signs from inns the raider drank up, and even tombstones from broken necropolises are given to the Mega-Gargant as proof of his prowess lashed. Many wear hoods of dark leather in imitation of city executioners, those fierce figures who deal out the only kind of justice a Gargant understands—but where the executioners take lives, the Gatebreaker destroys entire cities. A rune-carved door or an enchanted portcullis from a prized gatehouse might be worn as a ledgeplate, on the grounds that where it once protected a city's most valuable territory, it now protects that of its conqueror.
In combat, the Gatebreaker tends to swing the masonry and fallen statues of those civilized areas it has torn apart. He does so not out of a sense of pleasant irony in turning the works of humans, duardin, and aelves against their creators, but simply because they tend to be much heavier and more durable than the tree clubs favored by other giants. Strapped to a heavy chain, a fallen statue can make a devastating flail, capable not only of smashing down walls, but also—in those rare cases where the Gargant's sheer size isn't enough of a weapon—slither over the battlements to slay the to smash defenders to hide behind. When these "fortcrushas" are wedged between the battlements, they can then be pulled hard to reduce much of the curtain wall to rubble, leaving a gap which the giant can quickly exploit.