The Krudzu Hydra Hybrid was created by Robotnik Prime as part of his efforts to destroy The Great Forest and uncover the location of Knothole Village. While it turned out to be quite the menace, it was unable to stand being drenched in water and was supposedly destroyed.
Years later, however, the Krudzu Hydra Hybrid resurfaced after having assimilated the bodies of old, outdated Badniks. It had been hiding in Robotropolis since it's first defeat and had managed to survive the nuclear holocaust unleashed upon the city by Eggman in an effort to turn The Great Forest into a radioactive wasteland.
Doctor Eggman, who had never created the Krudzu Hybrid Hydra in his universe, destroyed it before it could kill Sonic. Eggman's reasons for destroying the vile plant-like robot was because it had been a product of Robotnik Prime's genius, not his own, and he couldn't abide Sonic dying at the hands of a machine that was not of his making. Despite Eggman's efforts, however, a sprig of the Krudzu Hydra Hybrid survived.
The sprig was later found by Eggman and Snively, who took it back to his laboratories and reprogrammed it to serve him. The Krudzu Hydra Hybrid was later fused with the body of an unused Titan Metal Sonic and was unleashed upon Team Fighters while they were pursuing the Death Egg Mark II across Mobius but the battle did not go in the Krudzu Hydra Hybrid's favor and it was pushed into the ocean, which destroyed the Titan Metal Sonic in the process, leaving it without a body.
The Krudzu Hydra Hybrid later appeared on the shores of what was once the Echidna settlement of Albion after having merged with a Crabmeat, making it impervious to water. When it finally entered the ruins of Albion, the Krudzu Hydra Hybrid called out to see if there were any Eggman-loyal forces in the area but instead stumbled upon the guns left behind by the Echidnas whom Thrash the Tasmanian Devil had banished to another universe and the deactivated body of Metal Knuckles.
Delighted by its new find, the Krudzu Hydra Hybrid abandoned the Crabmeat body it had been using and merged with Metal Knuckles' body and set out to find Sonic and his friends, who were already in Albion. The Krudzu Hydra Hybrid managed to sneak up on them while they were examining Thrash, who had been knocked into unconsciousness, Knuckles the Echidna and Team Fighters dueled with it but with the power of Metal Knuckles at its disposal it had become a true force to be reckoned with.
Knuckles was forced to leave the fight when Thrash woke back up and escaped from Albion through a warp ring, leaving Sonic, Amy and Tails to face the mad hybrid alone. As the duel waged onward, Sonic and the others managed to disable the weapons that came with Metal Knuckles' body, but what they had failed to realize is that the Krudzu Hydra Hybrid could assimilate any form of technology to enhance itself with and fused Metal Knuckles body with the abandoned Dark Egg Legion and Albion-made technology laying all across the battlefield.
It was then that Shard, who had been assigned to keep Team Fighters safe and make sure their mission was a success, made his presence known and after a brief tiff with Team Fighters ganged up on the Krudzu Hydra Hybrid, who believed that Shard would make a nice addition to its already screwed up, hybridized form. After managing to get the Krudzu Hydra Hybrid to release Tails and Amy, Sonic and Shard dragged the abomination all around Albion at super-sonic speeds.
When they came full circle, Sonic and Shard tossed the Krudzu Hydra Hybrid at Amy, who had her hammer poised to strike and watched as she knocked it through several ruined buildings. Before it could recover, a group of Devil Dogs tore it to shreds, reducing it to nothing more than Metal Knuckles' head being supported by the vines that made up the Krudzu Hydra Hybrid's true form. Not willing to give up, however, it tried to get back up but before it could Shard, Sonic, Amy and Tails destroyed the rest of its body, leaving only a sprig.
But as Sonic was preparing to "plant" it in a place where there would be no technology for it to assimilate, Shard called a time out and convinced them to hand the sprig over to him, so he could take it back to New Mobotropolis to see if it could be modified into an antibody capable of deroboticizing Sally. The Krudzu Hydra Hybrid has not been seen since.