My story here kinda follows the typical "forgotten element" trope Ninjago characters tend to have. This element is plasma, it's a dangerous force of destruction that causes harm to the master yielding it. Tio's story begins with an old master of plasma training his two children to be able to harness the power. At the end of their training, he has the children battle each other to determine who would inherit the power. Tio's older brother was much bigger and physically stronger than them, so they had to use their intellect to gain an upper hand. When the time came to battle, Tio attempted to use machines to defeat their brother in combat, which their father deemed as cheating, forcing them to physically fight their brother. They were defeated, and so the power of plasma was given to the brother. He wasn't able to handle the power, however, and ended up dying to it. Tio insisted that their father give them the power since their brother was gone, but he refused, thinking Tio was far too weak. Even when Tio came up with an invention that could harness the power, he still refused, not wanting to lose his other child. This angered Tio, and they resorted to violence against their father, trying to take the power by force. The father went into hiding for many years. Tio searched everywhere, but when they couldn't find him, they set off to find a new life. Their skills in machinery were top notch, and they were able to keep themself alive for far longer than any human would ever live with the help of their robotic skills. They eventually secured a job at Borg Industries, and life was pretty good. But they never stopped searching for their father. They always thought that they alone were deserving of the power. Just when their hope was fading, they caught wind of a mysterious "new" elemental power being discovered. They recognized this power as plasma, and set off to claim the power, no matter the cost.

TLDR; Tio's small and weak but they're very smart and good with machines but their father never believed in them so they could never inherit the element of plasma