In the time leading up to the Great Cataclysm, the Morbuzakh began to appear in the outer edges of Metru Nui. Its vines damaged and destroyed a number of buildings, and several Matoran mysteriously disappeared. When six of the city's Matoran became the Toa Metru, they immediately began the task of stopping it; and thanks to a vision of Toa Vakama's they had an idea how: find six Great Kanoka Disks hidden throughout the city with the help of six Matoran who knew their locations.
While the city's Vahki law enforcers proved to be the more prominent threat to the Toas' hunt for the Great Disks, Vakama did encounter Morbuzakh vines a few times and learned that they despised the cold. The Toa also discovered that the vines were controlled by a giant King Root, and putting the two together they realized that there was only one place the Root could hide unnoticed in the heat it thrived on: Ta-Metru's Great Furnace.
Taking refuge from Vahki in a forge near the Great Furnace, the Toa encountered a sort of breeding ground where the Morbuzakh grew its seeds. The seeds shot out and sprouted vines that ensnared the Toa; but they were able to escape and destroy the building. Entering the Great Furnace, they were halted by another of the Morbuzakh's defenses: waves of thorns shooting out at them. The six Matoran who aided them on their search saved them by merging into a Matoran Nui and bringing down the door that separated them from the King Root. After the Toa went in, the Matoran Nui split back into individual Matoran and they went their separate ways, only to disappear as so many others had.
When the Toa Metru faced the King Root, the Morbuzakh "spoke" to them telepathically, making them realize that it was no mere plant they were facing. It told them it intended to trap the Matoran in the center of the city and make the survivors its slaves. As the Toa were overcoming the shock of its announcement, it began to attack, launching thousands of its vines against them. Although the Toa fought bravely, their inexperience led them to tire quickly. Vakama realized they were fighting a losing battle and told the other Toa to surrender and drop their weapons. As the vines grabbed them and brought them in close, they activated the Great Disks, causing them to release beams of energy. The energy beams began to entwine themselves around the King Root, forming a sphere and slicing through its vines and branches. The Morbuzakh vines throughout the city began to crumble into dust; and when the energy sphere dissipated the King Root fell to the ground and disintegrated into nothingness itself.
In the following days the Toa Metru would learn more about the Morbuzakh's purpose. It had been created by Makuta to kidnap Matoran to place into spheres, where they would fall unconscious and eventually lose their memory. It was also instructed to drive the Matoran to the center of the city, where the Vahki (also under Makuta's control at this time) could more easily round up Matoran for the spheres themselves. The Morbuzakh's intention to conquer the Matoran, however, was not part of Makuta's plan.
Like the Karzahni plant, the Morbuzakh communicated using telepathy (though it tended to "speak" with a lisp, slurring its "s" sounds). It could control its vines like tentacles, and could shoot thorned branches and seeds. The seeds would burst upon impact into a mass of vines, ensnaring whatever they hit. In addition, the Morbuzakh drew their power from fire, gaining strength from intense heat. As such, it only made sense for them to choose the hottest place in Metru Nui-outside the Ta-Metru fire pits-as the location for their King Root and as an arboretum for their young. Fortunately, this also led to weakness to cold, meaning that Morbuzakh vines were particularly vulnerable to freezing Kanoka and the element of ice.