A long time ago, very long after Chernabog's imprisonment, but not long after Malefor was defeated for the very first time, there were two snake brothers. One was Hiss, a good-natured, if wimpy snake who wanted to be the royal adviser to King Richard. The other was a bold and brash snake named Fang who wanted to be important in the world and have a higher position than just an adviser. Hiss tried to tell his older brother not to dream up too big an ambition for it could lead to ruin in the end, but Fang wouldn't listen.
Meanwhile, the wicked Darkspawn lord, The Makuta, had just escaped the Banished Realms and wanted to control enough souls so he can conquer the United Universes for himself, and he needed a co-ruler with a dark heart in order to obtain these souls. Traveling around the worlds, Makuta eventually came across the young Fang during one of the boy's failed auditions to gain a position in King Richard's court. The demon approached Fang, telling him that he was destined to be more than just a servant in the kingdom. Why, with just the right guidance, Fang could be the greatest of all emperors and rule thousands of worlds in a great empire. All for the price of submitting into the darkness, and to become Makuta's pawn in his grand scheme to conquer the universes.
Fang considered for a while, then accepted, but not before telling his shocked brother that he was quitting the family forever. After Fang agreed to Makuta's demands, the Dark Spawn lord engulfed him a sickly green glow, which gave the snake the ability to use magic to his will. Makuta even gave Fang a spellbook he could use to learn all sorts of new powers. But there was a cost to this power. Makuta had secretly made Fang into his soul slave, and infused the personality DNA of the villains, Scar and Ruber, into Fang's heart, turning the snake into a carbo copy of the two villains in personality and voice. For you see, Scar was the prime shining example for which all villains strive to achieve a rank of power like him.
Makuta then gave Fang the starting point to create an empire by summoning up Darkspawn Bionicle warriors to serve as Fang's soldiers and mooks in the army. With this power, Fang immediately began to conquer worlds and recruit villains to his grand hierarchy. Makuta also desires the Kronus Stone, but for what reason is not known yet (spoiler prevention). As of now, Fang rivals Mirage and Dr. Nefarious as one of the great villain leaders of the worlds.